Rosenborg coach Aage Hareide said: "I have spoken to Heggem and said that he is welcome to join us in Rosenborg.
"First of all we are talking about our clinic - to get Vegard fit and healthy again. If he does that, he can start training with us.
"And if he is training with us, it could be an option to offer him a contract - maybe a contract where he gets paid for each match he plays.''