Toni has been outstanding for Roma since arriving on-loan, but still has 12 months left on his Bayern deal.
Rummenigge said: "I am not surprised [by Toni's impact]. Luca is a player of great quality and it's normal that he has started scoring again. He was motivated when he left Bayern.
"The relationship between Luca and Louis van Gaal wasn't good and unfortunately he publicly criticised the Coach. It was difficult to 'recompose' the relationship and the best solution for everybody was to sell Toni on loan for six months.
"He asked us if he could leave for Roma because he needed to play to be selected for the national team. It's a good choice. I hope he convinces Marcello Lippi and qualifies for next year's Champions League with Roma.
"The loan expires in June and Toni has another year of contract with us. It's too soon to say what will happen, but we have a great relationship both with the player and with Roma. We will find a solution."