Romo, who has been on the disabled list since April 15 after being diagnosed with a strained flexor tendon, had hoped to be activated this week. An MRI on Monday showed no structural damage.
"He'll have to build it back up so it will take a little while," Bochy said. "We don't know how long at this point.
"We were looking forward to having him back. He's our setup guy. It's disappointing because he was going so well. The good news is there is nothing structurally wrong. Hopefully it won't be too long before we get him back."
Romo, who is in the final year of his contract, has only pitched in 3 1/3 innings over four games this season. The former closer, who has 80 career saves, has a 2.70 ERA