"I feel free," Romero said before the series finale against the San Diego Padres.
The left-hander pitched 1 1/3 innings, allowing an unearned run on two hits, a walk and a passed ball by Chris Conte in Philadelphia's 5-1 victory.
Romero, who earned two wins in Philadelphia's World Series victory over Tampa Bay last year, retired left-hander Brian Giles opening the ninth, then made way for Ryan Madson. Romero pumped his fist and gazed skyward as he walked to the dugout, where he received handshakes from his teammates.
Romero was suspended after testing positive for androstenedione, a substance that Mark McGwire used in the 1990s that was later banned by baseball. Romero has sued the manufacturer of an over-the-counter supplement that he said led to his positive test.
"It has been a very tough road, but I'm still standing with my head up high and trying to just do my job," Romero said.
Romero said he's strong mentally but hopes people don't lump him in with steroid users.
"The human side, it's tough to understand you being accused of wrongdoing when you know in your heart you didn't do anything," he said. "But now I have to face the consequences of perhaps being judged by other people. I just hope that the people that are my fans, that are supporting me, spread the word and let the other people know, 'Listen, this is not just your typical guy who does steroids to cheat the game of baseball.'"
Romero lost $1,289,617 of his $4 million salary.
Romero sued Proviant and Ergopharm, the makers of 6-OXO and 6-OXO Extreme, in late April, arguing they misrepresented their products and ingredients and should bear blame for his being suspended.
Proviant Technologies has disputed Romero's allegations, and added the pitcher should take responsibility for his own actions. The manufacturer noted that each bottle of 6-OXO Extreme carries a warning label that reads: "Use of this product may be banned by some athletic or government associations [including military]."
While admitting there were things he could have done to prevent the positive test, Romero said the supplement bottles didn't have a warning that they contained androstenedione.
"It's a learning experience," he said. "But you just hope that the other people who were involved in this situation learn as well. It's not easy taking the blame of something when you have other people having some culpability in the matter and not being accountable for their actions. It's tough, but hey, I'll take it and move on."
Romero said supplements present a fine line.
"I just would like people to understand that what seems right for everyday people to do is not right for athletes anymore," he said. "I guess going to GNC for everybody is normal. For us, it's not normal. That's what I want people to understand, that testing positive is not being able to do the things that everyday people do to keep themselves in shape."
Manager Charlie Manuel said Romero gives the Phillies one more option in ultimately getting to closer Brad Lidge.
"We missed J.C.," Manuel said. "We can definitely use him. We'll pick a spot and put him in there a couple of days probably, kind of get him going. When he falls back into his role, he and [Ryan] Madson together, they kind of stabilize the seventh and eighth innings for us.
"J.C.'s real good at getting lefties out. He can get the ball up close to them. He can the ball in on them."
"That's big for any bullpen, especially our bullpen," Eyre said. "It's good to have him back. We missed him. He's a good guy to have around."
Information from The Associated Press was used in this report