The striker took his tally to 11 goals in 10 games with two fine efforts after Ryan Cresswell had opened the scoring.
The Shrimpers were easily able to make it 13 matches unbeaten as they moved up to fourth place in League Two.
Defender Cresswell put Southend in front in the 51st minute when he volleyed home his eighth goal of the season from 12 yards after Marc Laird's shot from Michael Timlin's cross had been blocked.
Paul Sturrock's side doubled their lead 10 minutes later when Tomlin swapped passes with Kevan Hurst before charging in to the box and heading home the midfielder's right-wing cross from 12 yards.
Tomlin was at it again in the 69th minute with the best goal of the night as he nodded in a chipped left-wing cross from Chris Barker following a number of successive passes.