Senior Trevor Hoxsie (Scarborough, Maine), who was brought down in the box on the play in question, converted the penalty kick to tally his third goal of the season and deliver the Hawks the victory.
The game was a balanced affair, with each team having nearly the same number of shots, and each keeper playing well.
Junior Matt Pils (Monroe, Conn.) made seven saves and has now conceded just one goal in three games where he, like the Mustangs, has a record of 1-1-1.
Roger Williams (3-0) saw senior Jon Pelloso (Wilbraham, Mass.) made five stops and earned his first and the team's second shutout of the season.
The home team had a chance to get their noses in front 15 minutes into the first half when junior Peter Sliva (Glens Falls, N.Y.) slotted a through ball for Michael Templeton (Charlestown, N.H.), but the junior forward couldn't beat Pelloso, who corralled the ball after it spun out of his hands.
With 22 minutes left in the half, Nick Rivas-Vasquez (Hamden, Conn.) found Templeteon with another good through ball, but Templeton, who was one of three Mustangs with three shots, sent his attempt swerving off to the right of the goal.
Pils made a diving catch to his left a minute later to stop a point-blank shot by Hawks freshman Trevor Sparda (Scarborough, Maine).
Mount Ida's best chance of the half came in the final minute of regulation, when they had a flurry of offensive opportunities. Carlos Rojas (Stamford, Conn.) slotted a shot from the left corner that Pelloso pushed past the far post and the Mustangs had three corner kick opportunities in the final minute. One of them resulted in a header attempt by Templeton that was pushed over the top of the net.
The Mustangs had the biggest advantage in corner kicks in the game, where they earned four in each half, while Roger Williams wasn't granted a chance from the corner flag.
Hoxsie had five of the Hawks' 13 shots, while Rojas and Dishawn Miller (Bristol, Conn.) each had three attempts of Mount Ida's 12.
Mount Ida has another non-conference test against a strong regional opponent next, this one on the road when they travel to Babson next Wednesday for a 4:00 pm game.
Roger Williams continues their road trip two days from now with a 12:00 pm game at in-state rivals Rhode Island College.