Hooker Issac Luke took over the goal-kicking duties to nail three crucial penalties and a conversion, and helped with the kicking in general play after the Warriors lost five-eighth Thomas Leuluai to a head-knock in the eighth minute.
"I didn't do any training this week so had to just get through training yesterday and it felt alright," said Johnson.
"I've just got a quad strain so just goal-kicking is probably the only thing I'm not quite ready for yet.
"I actually did it goal-kicking early on (against the Knights) and it just got worse throughout the game last week and we were lucky enough that we were up by a few points so I was able to come off.
"I'm happy I played the full 80 (minutes). It's nothing serious. I've been through similar things before. It's just the load of kicking that we have to do. I'll manage it, I'll be right."
Reeling from last week's record-breaking 46-0 defeat to Melbourne, the Roosters worked hard to limit time and space awarded to the Warriors attack.
Despite the injury, Johnson delivered when it mattered for his side after they had let slip several second-half try-scoring opportunities while clinging to a 6-4 lead.
Taking the ball 19 metres out he sliced between two defenders before stepping around Roosters fullback Lattrell Mitchell to cross the chalk in the 64th minute.
The Roosters hit back quickly with a try to Connor Watson helping narrow the margin to two, but the Warriors found the resolve to hold the visitors out to claim a gutsy win.
"They were desperate tonight and shut down a lot of space," he said. "When we got an offload they found their line really quick and it was probably frustrating at times, me not taking the line on, but generally it just wasn't on.
"I stuck with it, kept in the play, kept my eyes forward and an opportunity came and I took it.
"It's a good feeling. A lot of hard work goes into every week so to get rewarded, especially with a performance like tonight where it didn't go all our way, it's good."
The Warriors will look for a fourth-straight win when they head to Cronulla to take on the second-ranked Sharks on Saturday.