Manager Sean O'Driscoll does not want to break up his side but, equally, does not believe in denying ambitious players the opportunities of big money moves.
Leicester City and Wolves want Wellens, Sheffield United and West Bromwich Albion are keen on Stock, while Mills is wanted by Wolves, Newcastle United and Birmingham City.
All three have played a major role in Rovers winning promotion and surviving in this season's Championship.
Midfielder Wellens joined Rovers on a free transfer from Oldham Athletic two summers ago and is valued at £1.5m.
Stock, who won a first call-up to the full Welsh squad last season, cost only £125,000 from Preston North End three years ago and is worth £2m.
Defender Mills, 22, joined Rovers in a £500,000 move from Manchester City last season and was the subject of a failed £2m bid by Birmingham in the New Year transfer window.
Now the Blues have won promotion to the Premier League, manager Alex McLeish is likely to return with an improved offer and Rovers will demand closer to £3.5m for the former England youth international
The likely departures of Wellens, Stock and Mills will leave O'Driscoll with massive holes to fill this summer but, as Rovers have no serious debt, the majority of the money will be made available for reinvestment in the side.
O'Driscoll has already released five members of his first-team squad in order to release money for wages on new signings
Leicester City and Wolves want Wellens, Sheffield United and West Bromwich Albion are keen on Stock, while Mills is wanted by Wolves, Newcastle United and Birmingham City.
All three have played a major role in Rovers winning promotion and surviving in this season's Championship.
Midfielder Wellens joined Rovers on a free transfer from Oldham Athletic two summers ago and is valued at £1.5m.
Stock, who won a first call-up to the full Welsh squad last season, cost only £125,000 from Preston North End three years ago and is worth £2m.
Defender Mills, 22, joined Rovers in a £500,000 move from Manchester City last season and was the subject of a failed £2m bid by Birmingham in the New Year transfer window.
Now the Blues have won promotion to the Premier League, manager Alex McLeish is likely to return with an improved offer and Rovers will demand closer to £3.5m for the former England youth international
The likely departures of Wellens, Stock and Mills will leave O'Driscoll with massive holes to fill this summer but, as Rovers have no serious debt, the majority of the money will be made available for reinvestment in the side.
O'Driscoll has already released five members of his first-team squad in order to release money for wages on new signings