Yates' side bossed the opening 45 minutes and took a deserved lead after 24 minutes, midfield maestro Pack hitting home a 20-yard effort that squeezed past Fleetwood stopper Scott Davies.
They could have doubled their advantage before the break, Davies tipping Sam Deering's blast over the crossbar.
The Robins looked in total control, right up to the moment Fleetwood equalised through Junior Brown with a bullet header from a Ryan Crowther corner.
Yates said: "We were in control of the game. One mistake from a corner has ended up costing us.
"We've drawn a lot of games recently but this is one we really deserved to win. But you've got to stand up and be counted and do that for 95 minutes. Unfortunately one split second has cost us.
"We've had some great chances. But that's just the way our luck is.
"Later in the week we've got to try and take the positives from it but at the moment I don't feel like thinking about that."