The robbery was reported at about 8:20 p.m. at Gold Coin Motel in the 2400 block of Mendocino Avenue.
The clerk at the motel was approached by the three suspects who had come into the office and inquired about renting a room, police said.
One suspect restrained the clerk while another suspect removed cash from the register. All three then fled on foot, according to police.
No weapons were used and the clerk was not injured, police said.
Anyone with information on the robbery is asked to call the Santa Rosa Police Department's violent crimes investigation team at (707) 543-3590.