You can find them with low quality electronics. If you have sonar or preferable down imaging, just look for a rise in the bottom, goes flat for split second, then drops back down.. that's a road bed.. also there will be signs on the bank where there is a clearing in the trees. Another good way to find road beds are going on the satellite google maps, and you can see where roads just end, and the lake starts, then the road continues on the other side.