While the Solar 900 specs don't mention RVs, the general applications listed include fiberglass and metal joints, so that aspect should be fine. As for roof seams, it would depend on the roof material. If you have an EPDM or TPO roof, I would recommend a sealant designed for compatibility with those materials. If a fiberglass or metal roof, the Solar 900 should be ok.
As an alternative, try Geocel Proflex RV. It too is a tri-poymer sealant (the technology that Solar 900 claims) and it is specifically rated for most RV applications. And it is widely available as well.
2004 American Tradition; 2013 Buick Verano
Homebase in the Ocala Nat'l Forest near Ocala, FL