Well for roads I don't use the tablet - a tablet uses the pressure sensitivity so the roads can change widths. I want my roads to be the same width all the way through so I use the mouse. Then I just make some squiggles, nothing too tricky there. If you're doing something like a road map atlas style then use a pencil instead of a brush or, better yet, a vector program. You don't want your roads to be too straight because that doesn't look natural, the roads will follow up and down hills and along rivers so just some squiggles is fine. So I start moving the mouse and make a squiggle then move along kind of smoothly for a little bit then add another squiggle and so on...a mix of smooth curves and squiggles. The color of the road depends on the colors of the map, it has to blend in without being too obnoxious (except for road map atlas style, in which case you want them to stand out as much as possible). I generally make my roads a tan or low-opacity yellowish or a soft brown. Paved roads would, of course, be the color of what I think the surrounding rocks are so a gray or terra cotta or brown, etc. Scale also factors into how much squiggle you put in, continent or regional style will have a lot of squiggles while cities and battlemaps will be more smooth curves and straight lines. If you want to get all artsy-fartsy about it then you could try to have your roads be decorative and supply some sort of function other than travel. I talking about art class 101 things like contrast, shape, focal point, etc. I just sort of make things up as I go without worrying about those things, though. I just try to make them blend in and look natural.