I couldn't find any mention on the web for the "stock" roof material of that particular model and being 10 years old, it could have been replaced by now if there was any previous damage in the past. So my only suggestion to you would be to take it to your closest RV service shop and ask them if they would mind telling you what the material is. My local shop has been excellent about answering general questions like this and I've received a lot of advice from them regarding roof care, siding care, batteries, tires, you name it. I'm sure they won't mind since it's generally their slow season right now. I have a 2000 Roo myself and it's next service will be to put some new bearings and brakes on....or at the very least, have them checked. Who knows how far these things have been towed before we got them...
Where we've been:
2000 Rockwood Roo M-18 Hybrid
2006 Dodge Ram 2500 Auto 5.9 Diesel
Gone but not forgotten -1986 Rockwood 1003 PUP