This pack doesn’t really have roads.
He has “stickers” that function as the separator lines of a road that are laid out on top of the landscape plane which is dark black. The side walks are positioned in such a way on top to make the plane look like the width of a road.
In short, there aren’t any real roads in this pack. There aren’t many options for snap down roads available in general. The Quantum Theory pack has some roads avail which are re-usable, since they’re BP based, mostly for highways. There aren’t too many variations in terms of LOOK but its quick and easy to snap some together, but you can check the screenshots to see what they look like. The urban city has a spline approach, those roads are very clean looking, almost too clean and aren’t as easy to set up since you need to know how to use splines and move them around. Because they’re splines though, you can make the shapes however you want easier than fixed assets, but can be a real pain with collisions and visuals when you want to make non-flat roads like highways that go up and down with on ramps and stuff, there is also good looking crosswalk and road paint with this one.
Either way you’d have to buy another pack in order to use them. If you want to try your approach with the stuff in the Modular Building set, you can create a BP, add a static mesh, make it a long rectangle, and apply the road mat that comes with it. Then look for the “stickers” that represent the road lines and add them to that BP spaced out however you want. You won’t really be able to make bends in the road though unless you get creative with the shapes and make various sizes of the BP, it can get tedious with this method.