Torpey, playing against his former club, was shown a straight red card following a challenge on Louis Carey.
Laws said: "My players are hurt and disappointed. We've faced a team highly fancied to go up and given a good account of ourselves.
"I'll watch the two main incidents again on video, but we are convinced Showunmi was three yards offside and obviously interfering with play.
"Torpey was trying to get in front of the defender and insists there was no intention to foul him. I'll need to look at that before considering an appeal."
City defender Carey agreed with Laws, and insisted the sending off was the wrong decision.
He said: "Steve tried to get in front of me and caught me with an elbow, but he's not the sort to do it deliberately and he apologised immediately."
Robins boss Gary Johnson reckoned his side were deserving winners.
He said: "Overall I'm delighted, it was time for all the talking to stop after a good pre-season and we had to deliver.
"There were a few early nerves, but we hit the woodwork twice in the first half and restricted Scunthorpe to very few chances.
"Everyone is keeping their feet on the ground and there was no leaping around in the dressing room afterwards. It's just a start, but it was very important that we kicked off with three points."