While last year's finale was decided in overtime, the Blackbirds won the rematch handily, 90-73, behind C.J. Garner's 21 points and double-doubles by Julian Boyd and Jason Brickman.
Boyd, the NEC Player of the Year, finished with 18 points and 10 rebounds, while Brickman chipped in 18 points and 11 assists. Jamal Olasewere added 12 points for top-seeded Long Island (25-8), which shot 53-percent from the field.
Robert Morris' leading scorer, Velton Jones, was hobbled by an apparent rib injury suffered early on and was held to 10 points on 3-of-12 shooting. Lucky Jones led the third-seeded Colonials (24-10) with 14 points.
Robert Morris, the league champion in 2009 and 2010, won at Wagner on Sunday to reach its fourth straight NEC title game.
Long Island, playing on its home floor, had to rally to beat Quinnipiac in Sunday's other semifinal, but took control Wednesday with a 13-0 run late in the first half.
Olasewere netted seven points during the three-minute stretch, including two free throws to cap it for a 28-19 advantage with five minutes remaining.
Each time the Colonials inched closer, Long Island had an answer.
LIU's Brandon Thompson drained a three-pointer just seconds before halftime to counter Anthony Myers' trey, giving the hosts a 39-31 lead at the break.
Robert Morris again cut its deficit to five early in the second half, only to have LIU score 13 of the next 17 points. The spurt was finished off by Boyd's alley-oop slam off Garner's lob from halfcourt, yielding a 59-45 cushion with 10 minutes to play.
The closest Robert Morris got from there was nine.
LIU owns a 5-3 advantage against Robert Morris in the NEC Tournament...Robert Morris shot just 5-of-26 (19 percent) from behind the arc...LIU outscored the Colonials at the foul line, 31-14...Last season, the Blackbirds earned a No. 15 seed in the NCAA Tournament and lost its first game to North Carolina, 102-87.