Gilbert, 38, discussed her sexuality Thursday on CBS's "The Talk," where she is a co-host and executive producer, the Los Angeles Times reported.
Gilbert played Roseanne Barr's daughter on "Roseanne." Galecki, now on "The Big Bang Theory," was her boyfriend and later her husband.
On Thursday, she said she found Galecki "super-cute."
"We started dating and he would come over and we would make out and then I would start to get depressed," Gilbert said.
After she told him she had realized she was a lesbian and was trying to deal with it, Galecki kept her secret for years both from the "Roseanne" cast and from everyone else. She called him to warn him about the revelation she was planning to make.
"And he was like 'Yeah, no, of course' and 'I love you' and 'I think it's really important' and 'I'm so proud of you,'" she said.
Galecki even offered to hold her hand during the show.
Gilbert is now engaged to Linda Perry, a musician.