Gavin Mahon pulled the strings against his former club in his fourth outing for Boro, having joined on loan from Notts County last month, while Marcus Haber's 73rd-minute goal sealed the victory.
"First of all the formation we set up didn't work out as good as I hoped," Rosler said.
"We had three guys in central midfield and I thought we would get control of that.
"We were not competing. In the first half, we had only three or four players capable of competing with their physical strength and power and determination, so second half we made changes and obviously we looked much better.
"That sums it up a little bit, but I think Stevenage wanted it a little more.
"They don't want to get dragged down in a relegation fight but, of course, we have a lot to fight for.
"Second half was okay, but first half we didn't compete at all.
"I take a fair share of blame for the formation. It didn't work out as good as I hoped."
- Sports & Recreation
- Marcus Haber