The Arsenal man fired the Dragons level at Hampden from the penalty spot but blotted an influential display when he collected a second booking for a last-man barge on James McArthur in stoppage time.
Ramsey, already booked following a foul on Shaun Maloney, opted to take a quick free-kick with just seconds left on the clock only to under-hit his pass straight to Wigan battler McArthur.
Leading 2-1 after Hal Robson-Kanu had headed the visitors in front to punish the hosts - who led just before the break thanks to Grant Hanley's first international goal - Ramsey took no chances as his opponent hared towards Boaz Myhill's goal with a cynical foul.
But after the match he confessed he should have shown more savvy.
The 23-year-old, who now misses Wales' next World Cup qualifier with Croatia on Tuesday, said: "It was very disappointing - it's something I need to learn from.
"I should have looked up at the clock and let the goalkeeper take the free-kick. I had to (foul McArthur) in the end.
"It's disappointing to do what I've done after a great performance.
"I said sorry (to the manager) for letting the boys down. I'm missing the next game so I apologised."
The pre-match media circus had rounded on concerns that 25-goal Tottenham forward Gareth Bale may have to sit out the Group A clash amid worries over an ankle knock and a virus.
In the end, Bale was passed fit to start but limped off at half-time just minutes after sustaining a heavy challenge from the scorer of Scotland's first-half opener.
But even though they were forced to do without their talisman, Wales won through as Ramsey fired home an emphatic 71st-minute penalty after Robert Snodgrass had fouled Chris Gunter in the box while Robson-Kanu netted a powerful header three minutes later.
And Ramsey, who joined Snodgrass in an early bath after he too collected a second booking, insists that proves Coleman's side are not a one-man team.
He said: "We have some very good players who can do things, great things, and are comfortable on the ball. We proved that in the second half.
"Gareth Bale can do something out of the ordinary and that is what teams are wary of. But we showed we have a lot more to offer than just him."
Bale took to Twitter on Friday night to allay fears about his fitness.
He posted: "Just clearing the air... nothing wrong with my ankle. I came off at HT due to the stomach virus I've had all week. Should be ok for Tuesday.
"Great win by the lads tonight, hopefully we can take this on to the next game."