But the lead evaporated in a span of 80 seconds, and the Mountaineers eventually lost, 15-8, at Waldron Family Stadium.
The setback extended the losing streak for Mount St. Mary's to nine, a program record to begin a season. The team hasn't won since April 27, 2013, when it routed Wagner, 14-7, in the regular-season finale.
"We had a fast start, but we stopped executing our offense, and that's what really helped us early in the game," said junior attackman Mark Hojnoski, who paced the Mountaineers with career highs in goals (four) and points (five) after sitting out the previous four contests with a shoulder injury. "We executed and ran the plays right. For some reason, it all kind of fell apart. We have to bounce back from that."
The offense eclipsed the previous season high in goals set in losses to Manhattan (8-7 on March 9) and UMBC (17-7 on Saturday), but it has yet to score nine goals in a game this season; it had only one other multi-point scorer in junior midfielder Clayton Wainer (one goal and one assist).
The unit did not help itself Tuesday — missing the cage 17 times on 33 shots — but turnovers were a much larger problem.
At one point, the offense ended four consecutive possessions in the second quarter by turning the ball over on simple passes that were off target. Mount St. Mary's finished with 23 giveaways compared to Robert Morris' 11, which frustrated coach Tom Gravante.
"That is a key stat, and I certainly saw that," he said. "Five in the first quarter, six in the second, and it snowballed into a 7-4 halftime lead [for the Colonials]. There were a few times when we answered with a goal and we gave it right back to them. So we really couldn't stop the bleeding. It's a game of runs, and every time we thought we could get back into it, we didn't."
For only the second time this season, the Mountaineers scored the first goal of the contest. Just 68 seconds into the first quarter, Wainer passed the ball to Hojnoski, and he moved in from the right wing and bounced a shot past senior goalkeeper Brian Bohn (eight saves).
Sophomore midfielder Evan Gormley gave the team its first two-goal lead of the year when he raced down the left alley and beat Bohn just 45 seconds later.
And Hojnoski curled around the right post and scored for a 3-0 advantage with 6:35 left in the opening period.
But the Colonials scored three times in an 80-second stretch of the first quarter and the first three goals of the second period to take a 6-3 lead that they would not relinquish.
Robert Morris sophomore midfielder James Rahe led all scorers with six points on five goals and one assist, and sophomore attackman Luke Laszkiewicz added one goal and four assists.
The Colonials improved to 4-4 overall, earned their first win in three Northeast Conference games, and improved to 3-1 against the Mountaineers in their past four meetings.