Rosaryville is one of my favorite trails in the area. Combine well thought out lines, great drainage, and lots of fast twist and turns, this trail has everything you need, (except a good climb). Upon my last ride at Rosaryville a friend and I were pleasantly surprised by the addition of a new trail and some creative work done by MORE.
The new trail (which I am having trouble finding a map of) will leave you sniffing your fingers with delight.
Jackson from the MORE forums posted a link to this up to date trail map.
...you'll want to stick to the lime green trail and the blue. The purple isn't part of the trail system.
Much appreciated Jackson.