Robertson signed for the Broncos ahead of this season from Manly, and is now contracted to the club until 2014.
Robertson says he has been impressed with what he has seen at the Broncos this season.
He said: “I’ve been really impressed since coming here, it’s a very professional club and I’ve enjoyed my time here so far.”
“We may not be meeting people’s expectations right now but I really believe that we can kick on for the rest of the season and that will put us in good stead going forward.”
Wheeldon signed in May from Hull KR for the duration of the current season, and has sealed his future at the club with the same length contract as Robertson.
Wheeldon said: “I was delighted to get it signed. I’ve enjoyed playing down here, I’m playing every week and that’s what I came to do.
“The players and staff here are great, we need to finish the season strongly and we’ll go on from there.”
Coach Rob Powell was delighted to have secured the services of two key players for the long term future.
He said: “Michael has been a great influence around the squad since he’s been here. He’s a good leader and a good footballer too. He is the sort of person who will help the club to build and develop going forward.
“Scott has been a great addition since signing. He is one of the most consistent performers and we’re glad to extend his contract, which is fully deserved.”