Dave Mackay fired the Saints in front in the 51st minute only for Liam Craig to snatch an equaliser 20 minutes from time.
Lomas said: "I think we should have won it but it's always the way when you don't get that killer second goal.
"The double disappointment is that we switched off at a relatively standard free-kick and they got a little bit of fortune with a deflection which beat Alan Mannus but I thought we should have put the game to bed a lot earlier.
"We had enough chances to win a couple of games and there was some good defending from Ross County as well.
"But I can't fault the performance and attitude towards the game, we just need to be a little more clinical when we do get chances.
"The performance was good and we went about it the right way. I thought if we got the second we might have scored three or four but if you don't take your chances, it comes back and haunts you."