Fancied for promotion before the campaign began, the Latics have struggled to find their form and they lie in 18th place after goals from Kermorgant and Francis condemned them to a quiet flight home from the south coast.
"Overall, I feel personally embarrassed to the chairman and to the supporters that we as a group can’t deliver better results at this time," Rosler told the official Wigan Athletic website after the game.
"We’re lacking confidence; we’re lacking Championship qualities in certain units of the pitch, in power, strength and confidence to move the ball quickly."
The German hopes to have Callum McManaman back for Tuesday night's home match against Nottingham Forest with the Reds still unbeaten but looking to improve on goalless draws in their last two outings against Millwall and Brighton.
Stuart Pearce, speaking after the weekend game, said: "The players know that the performance levels need to be improved on massively."