The Rams got to within 60-57 on Xavier Munford's three-pointer, and then called timeout with 9.3 seconds remaining.
St. Joseph's guard Langston Galloway then hit one of two free throws with 6.6 seconds left to seal the win.
Ronald Roberts Jr. had 20 points, nine rebounds, and three blocked shots for the Hawks. It was his second game since he missed two with a back injury, and Rhode Island had no answer for Roberts inside.
"Our shots weren't falling and I was just trying to be down there, doing the dirty work and stuff like that, but we just grinded out and got the win," said Roberts, who shot 7 for 9.
Galloway added 15 points. He hit one three-pointer, giving him 293 for his career, one shy of the school record held by Pat Carroll.
Rhode Island did a good job of taking away the three-pointer from Galloway, who was 1 for 4 from beyond the arc.
"In the past we've lost these grind-out games, but this definitely big for our confidence," Galloway said.
Neither team showed much accuracy from distance. St. Joseph's was 2 for 14 and Rhode Island was 3 for 16 on three-point attempts.
The Hawks also hit just 21 of 38 foul shots.
Rhode Island didn't have the best shot selection in the first half, but somehow the Rams held a 30-27 advantage at intermission when Munford broke the tie with an NBA-distance three-pointer to end the half.
Guarded mainly by St. Josephs' freshman DeAndre' Bembry, Munford, who entered the game averaging 16.3 points, was held to five at halftime on 2-for-7 shooting. Munford finished with 16 points.
So the Hawks did enough to win, and coach Phil Martelli reminded everyone that winning is the main goal.
"It's a win," Martelli said. "We are not giving it back and not dropping our heads."