And 10 minutes before half-time England were punished for wasting chances as Roldan ruled Walker had intentionally made contact with Ben Youssef, Sassi's penalty powerful enough to beat the fingertips of Jordan Pickford and find the bottom-left corner.
Monday night saw England's most inexperienced World Cup lineup, in terms of combined appearances, since 1962 and it showed as they nearly fluffed their lines against Tunisia. The penalty was awarded after Kyle Walker caught Fakhreddine Ben Youssef with his arm.
England made a stuttered start to their 2018 FIFA World Cup campaign but beat Tunisia 2-1 at the Volgograd Arena on Monday to move up to second in Group G thanks to a stoppage-time victor from Harry Kane.
Harry Kane of England celebrates after scoring his team's second goal during the 2018 FIFA World Cup Russia group G match against Tunisia.
Tottenham's talisman reacted the quickest to score as Harry Maguire's initial header from a corner was saved.
'We've got this result over the past few weeks and that's because of everyone.
"I think we deserved the win", he said.
'We had to keep creating chances, we didn't play as well second half but they defended deep.
England had a legitimate case for a spot-kick at the other end when Kane was bundled over in the box as Alli headed against the crossbar.
In this year's tournament, the draw put two of the four longest shots in the 32-team field in Group G - Tunisia and Panama - putting the expectation on England and Belgium to reach the knockout stage.
Tunisia coach Nabil Maaloul selected striker Wahbi Khazri for his first match since April after an injury and wingback Ali Maaloul also plays despite picking up a muscle strain in a friendly against Spain earlier this month.
"In the Premier League it probably wasn't a foul, but in the World Cup it was", he said to the BBC.
Kane had given England the lead in the 11th minute after a bright start.