Heffernan, 28, told BBC Radio Bristol: "I'm enjoying myself down here and it was an easy decision to make.
"We're still eight or nine points off sixth place. If we start picking up a few wins, you never know."
Heffernan scored in Saturday's 4-0 win at west country rivals Swindon, impressing up front alongside Jo Kuffour.
And Rovers boss Paul Trollope added: "His sharpness is coming back and Saturday's performance was a sign of things to come."
The terms of the loan agreed with Doncaster mean that Heffernan will not be available if the Pirates reach the League One play-offs.