Clark (ankle) and Banfield (hamstring) both suffered injuries in last Saturday night's loss to Richmond, and after scans on Monday are both expected to miss three weeks.
The pair have been the Lions' leading goalkickers in 2011, with Clark kicking 19 goals and Banfield 15.
Rockliff said captain and focal point Jonathan Brown would need help from plenty of sources when the Lions play Fremantle on Saturday at Patersons Stadium.
"I think the whole team has to lift. I think we've got to get more midfield goals," Rockliff said.
"We don't seem to be running the lines and kicking as many goals as what other teams do so we need blokes like Daniel Rich, Jack Redden and James Polkinghorne breaking the lines and kicking them from 50-55m."
Rich (10 goals), Redden (nine) and Polkinghorne (eight) have all contributed this season, with Brown (13 from six matches) and Ashley McGrath (14) the other regular sources.
One player hoping to make an impact on Saturday is Rohan Bewick, who will return to his hometown after being traded to the Lions via the Gold Coast in the off-season.
Bewick, the nephew of Essendon premiership player Darren, has played nine matches, and showed plenty of run in a 17-disposal performance against the Tigers last week.
"When I first got listed this is the main match I wanted to play so it's really exciting," Bewick said of the Freo clash.
"I don't mind playing in the midfield, so if I can play half midfield and half forward I'm pretty happy. It (injuries) gives someone else a chance to kick some goals so hopefully I can get on the scoreboard."
Lions coach Michael Voss hinted earlier in the week that Irish recruit Niall McKeever could come in for Clark to offer more goalkicking options.
Rockliff said despite the Lions losing their third straight match last weekend, they will take some positives into the clash with Fremantle.
"I think we were in their face which was a good mentality for us and we attacked them which was good," Rockliff said.
"It was a little disappointing we let ourselves down but I think we saw signs of improvement from the previous two weeks.
"Fremantle play pretty well at home and they'll be disappointed with their effort last weekend. We're going over there with a mission to win and we know what we have to bring.
"It's not about them this weekend, it's about us."
Michael Whiting covers Brisbane Lions news for afl.com.au. Follow him on Twitter: @mike_whiting
