The Brighton keeper, who had a spell on loan at Hartlepool earlier in his career, escaped with a yellow card from referee Joe Ross when it could easily have been red.
Hartlepool's frustration was compounded when Roberts dived to his left to save Gavin Strachan's penalty.
It proved to be the turning point in a tight encounter as goals by Leon Knight and Chris Iwelumo clinched Brighton's seventh home win in a row.
Knight broke the deadlock with his 25th of the season on 68 minutes. The little striker steered in a volley from close range from a cross by Nathan Jones, who had been switched from the left wing to the right by manager Mark McGhee at the start of the second half.
Iwelumo made certain of the points deep into stoppage time with his third goal in four games since signing from Stoke, a downward header from Knight's centre.
McGhee said: "I am not sure if it was a penalty, but I am relieved that Ben did not get a red card. He could easily have been sent off. The game taught us that we need to be patient, especially when you have got a goalscorer like Leon.
"We are now five points behind Bristol City and Queens Park Rangers. I reckon we need to win our last six games to snatch the second automatic promotion place, which is a big ask, but we haven't given up hope.
Hartlepool manager, Neale Cooper, McGhee's former Aberdeen team-mate, felt Roberts should have been given his marching orders. "As I understand it that is the rule when you are the last man," he said.
"I thought we played quite well at times and we restricted Brighton to not many chances."