Lampard succeeded Rowett at Derby County last summer.
Lampard has taken Derby to the Championship play-off final in his first season in management, bettering Rowett's achievements at Pride Park last term.
The Rams had at one stage looked set to miss out on a top six finish, but continued their strong end to the campaign at Leeds United on Wednesday.
Lampard's men won 4-2 at Elland Road and 4-3 on aggregate to become the first club in the history of English football's second-tier play-offs to reach the final after losing at home in the first leg.
And speaking to BBC Radio 5 Live afterwards, Rowett - who remains out of work after being sacked by Stoke City - said of the 40-year-old: "His first managerial job - it’s not an easy job at Derby, as I can testify - to take this team, I know it’s only Wembley and he’s on the verge, but what you’d say is he’s done an incredible job.
'It's not an easy job at Derby and he's one game away from the Premier League'— BBC 5 Live Sport (@5liveSport) May 15, 2019
Former Derby County manager Gary Rowett believes Frank Lampard is doing an 'incredible' job. #bbcfootball pic.twitter.com/oBPbvP9t10
"Even if they don’t win the final, he’s done an incredible job so far.
"They started to have that dip, late December and January. As a manager, that’s when you’re tested. When you’re winning games everything’s rosy. As soon as you start losing games you’ve got to get that team out of that dip.
"I think that coincided also with (Mason) Mount coming back from injury, who is a big, big player for them, and probably (Harry) Wilson’s form kicking on. But you’ve got to credit Frank Lampard for that."
Derby will play Aston Villa at Wembley a week on Monday, with the winner joining Norwich City and Sheffield United in next season's Premier League.
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