Try the Canalway Trail (formerly termed the Tow Path or Canal Trail) from Long Pond Road to Spencerport. ~5.5 mi. All off road. No road crossings. All stonedust.
Alternatively on the eastside of Rochester from Main St., Fairport to Macedon Lock No. 30, ~8 mi. asphalt to stonedust. All off Road.
Oh! I forgot the trailer park at Waynesport Road might slow you down. Main St. Fairport to Canal Drive West (western end of the trailer park on the Canalway Trail, ~4.4 miles within your time limit. Stonedust surface, all off road.