These are some very detailed directions. It should take one hour and 15 minutes or less from Manhattan on a good day.

From the east side, take the FDR Drive north to the Willis Ave. Bridge that takes you to the Major Deegan Expressway. (Get into the left lane once you're on the bridge as it's a left lane entrance onto Deegan.)

Take the Deegan to I87, i.e., the New York State Throughway. Take it over the Tappan Zee Bridge all the way up to Exit 16 (which is very far after Exit 15). There are a couple of tolls along the way.

Exit 16 puts you on Route 17 (also called Route 6) "To Middletown, Goshen, Monroe."

Your second exit off of 17 is to Washingtonville/Monroe, which is Route 208.
Get off at 208 and at the end of the exit ramp, take a left. Cross over the highway and follow 208, which, at one point sort of curves to the right and takes you between two gas stations. Make sure you don't go straight when it curves.

Your next light is 17M. You'll be facing the Monroe Diner. Make a left. Go two lights (you'll pass the Shoprite) and make a right onto Lakes Road.

Wind your way up Lakes Road and watch the lake switch from your right side to your left. You're going to drive about three miles. When you pass the American Legion lodge on your right, you're very close. When you pass a "Walton Lake" sign on your right, you are painfully close. On the left just a teensy ways up you will see School Road. Take a left and go all the way up to the top of the hill where, on your left, you will see a sign that says, "Rosmarins Day Camp and Cottages." If you get lost, you can call the Rosmarins Office at 845-783-7222