The 23-year-old joined Sunderland on Tuesday on a five-year deal after limited first team opportunities in his two-year stint at the Premier League champions.
"I would probably say don't sign now, I'd say get as much football as you can," Rodwell, who stood out at his first club Everton, told reporters when asked for his advice to teenagers.
"The first thing I'd ask is, 'how good are you' You just never know - you could go there, do really well and be winning league titles and everything.
"But just because you're English and young it doesn't mean you're not going to play for Manchester City.
"I would just say weigh up your options and ask yourself if you want to be playing regularly."
Rodwell will link up at Sunderland with former City winger Adam Johnson, who was also critical of the champions' treatment of young English players when he left Manchester.
Capped three times, Rodwell's last international appearance came in a friendly against Brazil in June 2013.