Dylan Willick, Chase Souto, Kale Kessy and Aaron Macklin also scored for Kamloops, which now leads the second round, best-of-seven series 2-0.
Games 3 and 4 are Tuesday and Wednesday in Kamloops, B.C.
Myles Bell, who opened the scoring with a power-play goal at 1:35 of the first period, replied for Kelowna.
Jordon Cooke stopped 33 shots for the Rockets, while Cole Cheveldave made 29 saves for the Blazers.
Ranford made it 1-1 less than two minutes later at 3:11, with Willick making it 2-1 with his third of the post-season on the power play at 9:47 of the second.
In the third, Souto made it 3-1 at 5:06, with Kessy burying a rebound at 12:05 and Macklin closing out the scoring at 18:48.