Ahead at halftime 35-32, Cleveland State started the second half on a 21-7 run to break open the game and take a 56-39 lead with 13 minutes left to play. Mason, Kamczyc and Lee each hit 3-pointers during the run.
Cleveland State shot 57.7 percent (15 for 26) in the second half while holding the Redmen to 32.3 percent (10 for 31).
The Vikings outscored Rio Grande 12-2 on fast-break points in the second period.
Dominick Haynes led the Redmen (4-10) with 17 points.
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.