The Gridwall at Billboard and the Hideway are climbable in the winter on sunny days. Red corners area is also sunny, but when the sun is very low in the sky (end Nov to sometime in Jan) the wall never sees the sun. Parking can be problematic if there is a lot of snow. We usually use the Timp Cave parking or the pull-out to the camping loop and hike the road to the trailhead.
In Rock Canyon, the Superbowl wall is climbable. The School room (Ogden) is west-facing and climbable; however, the approach is sketchy if it is snow-covered.