Offline someone has alerted me to 6 more examples of the SR number changing at the county line. These are just northwest of the US 221-460/VA 220 ALT intersection...
Cortland Road (Botetourt SR 1464/Roanoke SR 1003) — SR transition is unposted.
*Orchard Park Drive (1459/1048) — unposted
*Gala Drive (1453/1025) - posted
*Rome Drive (1456/1024) - posted
*Hillview Drive (1420/1011) - posted
*Laurel Ridge Drive (1444/1447) - posted
Most of these 6 are posted -
https://goo.gl/maps/e8PeZnVR7RmThe Botetourt side of the neighborhood came first. When it was connected into Roanoke County my guess is that Botetourt didn't feel like renumbering them to numbers Roanoke had available. Roanoke ended up using numbers it had once used long ago.