Trinidadian Roti and Pastille
This weekend is the West Indian day parade in Brooklyn. I assume that you were planning on attending! Street vendors are bound to carry what you're looking for.
Also, the neighborhood of Crown Heights is home to a large Trinidadian community. There are roti shops up and down Nostrand Avenue between Atlantic Avenue and Eastern Parkway. To get there, take the 3 train to Nostrand Avenue and walk north on Nostrand, against traffic.