Hello, your question about Roads is a good one, and one that as 'kinda' been brought up by me before.

Humans (and dwarves, elves etc) like all animal species, will do their utmost at an instinctual/subconscious level to conserve energy when traveling. This means, they will try and take the most direct route from point A to point B, or as straight a path as possible. Things like small hills and gullies will be skirted/circumvented if the horizontal distance's energy expenditure is less than the energy expenditure of going over/down through the hill/gully.

The above is why I hate seeing city maps with individual buildings with wide yards in fantasy city maps. In days past these would have never occurred as realistically people would have built the same buildings much closer together as they would have spent less energy (at a time when nutrition was not as well as what we have today) to traverse the city. The yards would be almost non existent as people would chose to cross that open space to reduce the time/energy output to get from A to B.

So, where does that leave Roads in an Overland map? Roads will stay mainly on the plains, flat areas. If they do go into hills it will not be a straight on approach but at an angle where the rate of incline will be gentle (think of what consumes less energy, a flight of 5 steps over 4 feet or a 15 foot ramp). Roads will also follow rivers for the most part, cutting across the land only in places where a river's course will double back to itself in a short distance. This allows easy access to water for travelers and their livestock, and when it does cut across open land, it will be because either another source of potable water exists or the distance is such that the river will be reach again after a short time so less water must be carried (that energy expenditure thing again).

When a road DOES cross a mountain range this is done at a Mountain Pass:

In a range of hills or, especially, of mountains, a pass (also gap, notch, col, saddle, bwlch (Welsh), brennig or bealach (Gaelic)) is a path that allows the crossing of a mountain chain. It is usually a saddle point in between two areas of higher elevation. If following the lowest possible route through a range, a pass is locally the highest point on that route. Since many of the world's mountain ranges have always presented formidable barriers to travel, passes have been important since before recorded history, and have played a key role in trade, war and migration.

So, roads from one side of the range will often join at the point of where the pass enters/exits the mountain region, and by proximity likely the location of a fortress/town or other community of importance.