Trailing 41-35 at halftime, the Highlanders outscored the Bears 27-10 to open the second half.
After the Bears were within two, 74-72, with four minutes left, Jaylen Bland made a 3-pointer and UC Riverside (9-5) scored the final seven points to notch its fourth win in a row while the Bears (2-9) dropped their sixth straight.
Johnson, a freshman, picked up his first double-double. Bland added 16 points, though he was only 4 of 13 from the arc. Gentrey Thomas added 17 points on 7-of-8 shooting and Alex Larsson 10 on 5 of 6. The Highlanders shot 53 percent and are at 51 percent during their winning streak.
Phillip Carr had 18 points and eight rebounds, Antonio Gillespie 15 points and Cedric Blossom 14 for the Bears.