According to the MTA , there is Roosevelt Island F Train Service to and from Manhattan this weekend.
Keep your nose and mouth covered while riding with us. You’re helping stop the spread, and taking care of your fellow riders. pic.twitter.com/R9jrqhlNY7NYCT Subway. Wear a Mask. Fill out the Census. (@NYCTSubway) August 28, 2020
New York doesnt work without mass transit.MTA. Wear a Mask. Stop the Spread. (@MTA) August 26, 2020
The pandemic has left us in dire financial troublethis is the most difficult challenge weve ever faced. Without major federal assistance, we wont be able to continue moving New York. #SaveTransit pic.twitter.com/1JTsVpmEqq
There is a Roosevelt Island Tram Cabin 20 passenger Covid-19 Social Distancing limit. 
Here’s the NYC Ferry Roosevelt Island Astoria Route Schedule which now extends to East 90th street on the Upper East Side. 
Also, Roosevelt Island has a new transportation option with the recent addition of Citbike docking stations.