There is a nice trail system just north of Roanoke. Its about 30-45 minutes north on 220. Its called Eagle Rock. I'm 95% sure they allow 3-wheelers...there are no warnings in the brochure, nor are their any signs at the trail-head. There are plenty of trails there to ride all day and not see the same trail twice. Its on the top of a mountain with great views. All the trails loop off the main one and they are well marked so you cant get lost. There are some great mud-holes there too....a couple are about 1' deep or so.
They close between March 20-something and June (I think they allow hunting these times.
And speaking of being on a mountain...if it has been raining...you better have 4WD if you are towing a trailer. And if your vehicle is low to the ground...you are not going in or out without some body damage. You have to travel the last 4-5 miles on an old fireroad up the side of the mountain. We were in a F-250 Crew Cab Deisel with a 20' trailer carrying 4 large ATV's. There was plenty of room on the road for it....but you'd better not meet up with someone going the other way.
If anyone is going up there sometime soon...give me a shout...I'll see what I can do