Two quick points:
1. If the roof is wet, whatever needs to be done up there can usually wait until the roof is dry. The only time I nearly fell from an RV roof was transitioning from the roof to the ladder (coming down) and the roof was wet.
Lesson learned. I figure (but can't prove) most falls occur when transitioning from/to the ladder. It is true in the airline industry, so stated in the training video they make us watch once a year.
2. Put all your stuff in a bucket, and haul the bucket up with a rope. One end of the rope tied to bucket handle, the other just tossed over your shoulder. Or throw one end of the rope over the RV. NEVER try to haul tools up there in your hands while climbing a ladder.
See picture. All that stuff came up and went down in the bucket.
I just had the notion someone was going to fall off a ladder this weekend.