That's assuming you even earn the right to build roads in the first place, which isn't nearly guaranteed.

I think a hotkey would be the perfect solution.

I'd almost want an auto-build road function for units. Click it, unit builds roads where ever it walks. Click it again, this turns off.

I just had a situation in my latest 0.85 LH game where one of the cities I built didn't connect with my other cities, as there was a road from/placed by another empire next to the square where I placed this city.  Yeah, I SUPPPOSE I could go through the other kingdom's city, and go the LOOONG way around to get to my nearest city, but that adds about 20 squares or so to the commute.  And I haven't actually explored the enemy's roadbuilding network as of yet, so I can't know for sure, but I do know where another road heads off into the unknown about 10 squares to the south of this city, where my nearest city to this new city is located)...

AGAIN, I'll say give us a perk/trait that gives us the ability to build roads in unit design, and this won't be a problem.  The race that gets 'roadbuilding' for free can build roads without this trait, but other races have to learn the appropriate tech and take up a perk slot on their units to do so.  This sounds balanced to me.

And this would be in addition to the auto road building that we already have, not to replace it, although I wouldn't mind an option to 'turn off' auto roadbuilding in game options.

Have you guys noticed that in the commander tree, road building now has no prerequisite? Your prayers have been (semi-) answered - commanders now make roads at level 3. 

Yes, commander, level 3 does allow roadbuilding, and on a horse, can lay a lot of road in a few turns.  However, what if your sov is not a 'commander,' and none of your hero selections come up as commanders?  ouch city.  Henchmen and scions address this, but come way too late.  Agree, make it a trait, or make it a hero promotion choice that is outside any of the profession 'trees' so ANY hero can choose it upon level up.

The right road can win you a war.

No real point, as the other bonuses commanders get are so much better- Admin III or the Command line are just much better.

Admin heroes are kinda limited to boot so you don't really get 3 of them.

Necardan-

Mounts+Tireless March+road building = attack almost whenever/wherever you want. 

The right road structure means defenders can respond to incoming troops in 2-3 turns instead of 3-8, and possibly not arrive in time. Sometimes the AI will attack 2-3 turns after declaring war, this can be huge.

I'd recommend you play as Capitar, and design some custom road building scouts. If you build roads as you scout out the map from early game, I think you'll see the huge mobility difference. 

i always wondered why they didn't just unlock the road building trait at economics, instead of (or in addition to) auto-buildng roads to outposts. would make perfect sense to me. capitar still has the advantage, since they can do it from the start; an early admin hero can still give you the ability early on if it's really important - and if it's not a big deal, you just get it later towards the end of the civ tech tree. i think that could work al right for everyone.

Unlocking the trait for troops at economics or maybe construction sounds like best idea, and it should be a toggle (though move rate should be reduced to 1 when building roads)

Making it a toggle instead of manual would be easy to do (You have it for explore), and would solve the micromanagement issue- the key would be training the AI to use a cheap unit to build roads.

(Cue huckster/infomercial voice)

Roads, aren't roads cool?

Do you love using roads, but can't use them to get between all of your cities because they travel through another Kingdom's cities?

Or having roads taking long side jaunts between your cities, increasing your commute time?

Sure, you could wipe out your neighbor, but who wants to deal with that hassle?

Introducing: The ACME Roadbuilding System!  Yes, you too can build your own roads!

(huckster voice off)

OK, after multiple auto-roadbuilding fiascos, I enabled mods and added the following code/file to the documents->my games->Legendary Heroes->Mods->Data Folder.

You can use notepad for this.  Just paste this code into notepad, and save as roadbuilding.xml (or whatever other title you want).  Make sure you save as an .xml file in the save options, not as a .txt file.

This is a work in progress, as I still want to add some additional requirements (population, resource requirements, etc.)

Note that I made Trading and Construction the prerequisite techs.  You can certainly change these fields to other prerequisite techs, but these techs seemed to make sense to me.  If you want roadbuilding from the start, simply delete the prerequisites.

Also note the -1 to movement.  This slows down the pace of roadbuilding, hence making Capitar's roadbuilding ability more valuable.  Also, I'm undecided on the costs and such (12 turns for training, 50 cost), plus, as mentioned, I still need to add resource requirements and such.

If I could figure out how to code a 75% reduction in movement (so that horses wouldn't increase this over 1 MP, should you choose to upgrade to horses), that'd be fine.  I also thought about requiring horses for roadbuilding units, but I haven't dug that far into prereqs yet.  Again, the goal here is let Capitar keep their roadbuilding advantage, but let the rest of us fix AI weirdness.

Once the prerequisites are met, this should appear next to the scout ability icon/armies header in unit design.

Consider this an eWIP for now.  I've tested it and it works, but again I am still working on balancing/better implementation of my concept.

That isn't what a lot of people have been asking for, hence the unit trait, which IS what a lot of people were asking for.

Quick update:

I still haven't figured out how to 'trip' the mounts slot, to prevent adding of horses/wargs/etc..  So said units can still select mounts when available, and end up moving 3 squares a turn, and building 2-3 squares a turn, which is NOT what I was going for.  I did add a horse resource requirement, along with a population requirement (will post relevant code after a little more playtesting).  Again, my goal is to limit this to 1 Move per turn, so that races which select/have the roadbuilding ability are still at a significant advantage.

Do any of you modder types have a suggestion on how to 'fill' the mount slot, as a trait?  I thought about making this equipment instead, but then this wouldn't require a trait slot, which is what was arrived at.  FYI, the idea here is that you need work horses to help build the roads, so the horses are carrying equipment, pulling improvised graders, etc.  Again, this is to 'balance' the trait against the roadbuilding ability of certain races.