Lee Novak powered home unmarked from 10 yards just before the half-hour mark to give the hosts a deserved half-time advantage.
But Rovers battled back to grab a point courtesy of Cotterill's 30-yard thunderbolt 12 minutes from time.
"It's a fantastic strike," said Dickov.
"We know David's got that in his locker from the goals he scored last year. It's something he practices a lot, technically he's very good.
"He's a had a few this year which have gone wide and over the bar so I'm delighted for him."
Dickov was happy with an improved display from his side after the break following a disappointing opening 45 minutes.
"We don't want to get beat in games and limp off the pitch at the end of it. If we're going to get beat, at least get beat having a good go," he added.
"I didn't feel as though we did that well enough in the first half.
"My players know what I'm like as a manager, if they go out there and have a right good go then I'll back them all the way - win, lose or draw.
"But I keep saying to them if you do have a go and try to do the right things then you've always got a chance of getting points."
- Sports & Recreation