The defender came through a 4-3 victory against a young Reds line-up at the Memorial Stadium after recovering from a knee injury which has kept him sidelined since October last year.
With Steve Elliott rated doubtful for Saturday's opening-day clash with Leyton Orient, Coles' return is a timely boost for the Pirates.
Trollope said: "Danny coming through his first 90 minutes for nine or 10 months was a major bonus for us.
"We still need to look after him and can't ask too much too soon, but he can be a major player for us this season."
Byron Anthony scored twice and Rickie Lambert and Jo Kuffour were also on target as Rovers ended their pre-season schedule with an entertaining victory.