The Hammers boss said: "The manner in which we let in the two goals summed up our first half performance, which was very disappointing.
"It was a lot better in the second half but the game was lost by then.
"No excuses were offered by either of the lads involved in the two goals and they both know that we can't afford to let in goals like that at this level.
"To be fair, Shaka Hislop has been superb so far this season but he was very disappointed with his part in their first goal.
"The second goal was a weak header by Rigobert Song and the level we are playing at, those errors shouldn't happen."
Roeder was also critical of his midfielders, saying: "We never got close to them in the midfield area for the first 45 minutes."
But the Hammers boss had some sympathy for new signing Tomas Repka, who was sent off after receiving two yellow cards.
"I was disappointed that he was sent off and it all hinged on the first booking, which was silly really.
"He tapped the ball away to where he thought the free-kick should have been taken from - it's not as if he ballooned the ball down the pitch.
"As for the second booking, Dean Windass seemed to be tugging him just as much and I'd like to see the video replay of that."
"But Repka will be fine for us. He's a Stuart Pearce type, very competititve and he uses the ball well when he's got time. It's just disappointing that he'll miss our game up at Everton."
With Wednesday's home game against Aston Villa postponed, Roeder admits it will be nice to finally get back to Upton Park next Sunday, albeit to face a Newcastle United side high in confidence after scoring eight goals in two games.
"Psychologically, it's never nice to be bottom of the league at any stage of the season, but we've got a long week ahead of us now and time to work hard on the training ground to put things right."
After managing just one goal in the first four matches of the season, Roeder expects to welcome back Paolo Di Canio for the visit of the Magpies next week.
He explained the Italian's continued absence at the Riverside: "Paolo got a kick on the ankle at Derby, around the Achilles tendon area. The swelling didn't go down in time for today but he had a scan on Friday and I'm sure he'll be fit in time to play against Newcastle."
Commentating on latest transfer speculation, Roeder added: "Trevor Sinclair is going nowhere - we're not looking to do business with Sunderland.
"As for the story linking us with Ray Parlour - it's just speculation."