Alison from the blog "Run With It" apparently knows what a number of NYC runners know... namely that Roosevelt Island is a great place to run. In fact she saw Roosevelt Island listed on Active.com's list of 10 great places to run in NYC.
The list in order is (1) Central Park, (2) Jacqueline Kennedy Onassis Reservoir, (3) Riverside Park, (4) East River Walk, Carl Shurz Park, Bobby Wagner Walk, (5) Roosevelt island, (6) Brooklyn Bridge, (7) Prospect Park Loop, (8) Madison Square Park, (9) Battery Park, Hudson River Park, and (10) the Brooklyn Heights Promenade. As a non-runner I can't comment on these sites but I can say I plenty of local residents and visitors running on our island so Alison is in good company when she visits Roosevelt Island.
You can't beat the views, the promenades surrounding Roosevelt Island offer a safe, quiet place to run in a City that sometimes is a bit too busy when you like to get into a running groove.