What websites, publications or real estate professionals would you recommend to people looking for rentals in Roosevelt Island, New York City?

There are only 4 places to rent, and they all have rental officies
Octagon (across from 79th st in Manhattan)
Manhattan Park -10,20,30,40 River Road (across from 70-73 rd st in Manhattan)
Roosevelt Landings - (across from 65-68 st in Manhattan)
Southtown - (across from 62-63 st in Manhattan)

I would try Craigslist to start. If you're thinking of working with a broker, then I would do Citihabitats. They're the least skeezy, in my opinion. And, you'll find an apartment pretty fast with them if you know what you're looking for (i.e. elevator or walkup, whats the max rent, how close to transportation you need to be, etc.).