I had one small road left for the longest time. Couldn't figure it out. Let my ex girlfriends little brother play and told him to find it. Little shit found it right away. Take a screenshot of your map and post it in the comments. Maybe we can help.
Cheers guys... yep ive zoomed in everywhere and cant find places ive missed.... only been playin it 1 week so far so its early days for me... just thought I'd ask lol..
None are hidden, all are shown, it may just be a small patch you missed, try zooming in on the map, you can also use the magnifier the xb1 has to help, have a pic, maybe I come take a look