Assombalonga had gone five matches without scoring but got back on track with the well-taken brace against the Gulls.
And he was only denied a hat-trick - and the matchball - by an offside flag.
"I hadn't ever gone five games without scoring before and it wasn't very nice, so ending the run was fantastic and I'm really pleased," Assombalonga told Southend's official website.
"I kept on working hard when things weren't going my way because when you do that I think you get your rewards. Mine came at Torquay.
"The linesman obviously didn't want me to have a third goal. He put his flag up even though I had come from the blind side of the defender, so I'll have to save that for another day now."