I'm not fond of getting on the roof and DW won't. I used a 6' stepladder and a light, 'dollar store' broom to sweep my slide last year. I climbed the ladder at either the front or the rear of the slide (so I had a slide side and the trailer side close to me) and swept as far as I could reach. I then moved the ladder to the other side of the slide and finished the job.
We have a long bed pickup so taking the ladder is no trouble. There are compact ladders and some folks secure a stepladder to the trailer's ladder.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.