The 24 year old only returned from a lengthy absence with a broken scaphoid in last weekend's 38-28 loss to Celtic Crusaders, a reverse that dropped Fax from second to third in the table.
But Penkywicz finished the game in considerable discomfort after damaging his jaw, with boss Matt Calland initially fearing his most potent attacking player could have been facing another lay off.
A trip to the dentist eased those fears though, with Penkywicz confident of making the selection cut at Post Office Road.
"It's settling down a bit now and I'll be fine for Sunday," said Penkywicz.
"I've loosened my wisdom teeth, but it won't stop me playing.
"It's an important game for us and I think everyone wants to be involved."
Just how important the fixture is will become clear tomorrow evening, when Celtic host table toppers Salford at Brewery Field.
A win for the Reds would open the door for Fax to snatch the runners up spot with a win over Rovers, while a Crusaders victory would leave Penkywicz and co confirmed in third.
"We will know what we have to do, but it's only going to help us if Salford can do us a favour tomorrow," said Penkywicz.
"I'm not so sure what the chances of that are, because I've heard they are only travelling down on the day and it's a game Celtic probably need to win a little bit more.
"Hopefully, they will get the right result and then it's back in our hands for Sunday.
"Either way, we want to go into the play offs on the back of a win."
Penkywicz is likely to combine with former Warrington number nine Mark Gleeson for the second time on Sunday, with Fax's captain admitting the presence of the former England man makes his own job "easy".
Gleeson is guaranteed a hot reception after turning his back on Rovers to head to the Shay last month.
"Mark's a class player and having him on the field makes my job easy, to be honest," said Penkywicz.
"If the forwards can do their job and get us some go forward, I'm confident we can do some damage off the back of that."
Calland will name a squad later today, having assessed a staggering injury list that stretched into double figures after the clash with Celtic.