With a stop in DC, I'd do this route to RI
I-270 to I-81 at Hagerstown.
Continue up I-81 to I-84
Stay on I-84 to the Mass Pike
Take Rt 146 south out of Worcester (rhymes with mister) to I-295
I-295 goes around Providence and will get you pretty much anywhere in RI.
When you get onto Rt146 in Worcester, you're gonna say "What did this guy do to me???". Don't worry. Both ends have a business district, but in between it's 2 lane divided highway with very little traffic.
Alternately (if you're going to southern RI, like Pt Judith)
Above, except take I-84 to I-691/CT66 to Middletown
CT 9 south from Middletown to meet I-95 in Old Lyme.
RI border is about 1 hour from there.