It's a rather dangerous position to be doing forearm wrist curls. You could lose your grip easily and let it drop on your head. Otherwise, it would be a decent forearm workout. But for me, the triceps would fatigue much faster than the forearms would. This would make my forearm workout incomplete and rather pointless.
If you roll slow enough, it shouldn't affect your tricep workout. But I recommend just doing wrist curls afterwards. This is safer and you can focus on really hitting your forearms hard after your tris. However, if you can keep your form strict and both muscles fatigue, it would make for one hell of an exercise.