We traveled north on 81 two days ago, from Roanoke to I-66. Road is fine from a condition standpoint. As someone noted above, there is construction just on the north side of Roanoke but not that big a deal. Traffic was very heavy, but mostly due to the high percentage of trucks.
Someone mentioned Blue Ridge Parkway as an alternative. It is a VERY leisurely ride..... Also, they are paving the parkway which caused us to sit for 20-25 minutes at one point. We drove north on the parkway from I-77 to 220 (just outside of Roanoke). They are paving about 30-40 miles south of Roanoke. Unless you don't mind the new tar & gravel (not asphalt) and the lengthy wait, stay on 81. Wasn't a big deal to us, we wanted to take our time an enjoy the views from the parkway.
Regards.
Chuck