The Town of Rockland is in Sullivan County, right next to Delaware County. It is in the heart of the Catskill mountains and very pretty. Roscoe is actually one of several small hamlets that make up the "Town of Rockland".
It is very popular with fly fishermen, and many New Yorkers (from the city) go there year round for fishing and then hunting in the winter.
Roscoe itself is a fairly small town, not overly prosperous looking, but the people are friendly.
My dad is from Delaware county, and growing up was pretty hard. The main jobs in the area were farming and the railroad. This was in the 1930's and 1940's. It is one of those places that kind of stays trapped in time in some ways.
Here are 2 sites I found that might help you. http://www.historicaltownmaps.com/store/products.asp?p=315http://en.wikipedia.org/wiki/Roscoe,_New_York
Good luck in your search!