Is it a rubber roof?
You can use a fairly strong bleach solution on rubber and mix it with a good detergent as well (first check the label to make sure bleach can be mixed). Pine tree sap can be removed with isopropyl alcohol.
Despite the hype you will find on numerous RV sites, it is permissible to use mineral spirits sparingly to remove some stains or gunk, but do not allow it to soak in. Mineral spirits will loosen the glue that bonds the rubber to the roof, so use it as a last resort only. Just dampen a cloth with it and rub the spot - do not pour it on or soak the spot.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL