Fawthrop, who has just been appointed manager on a permanent basis at Ashton Gate after taking over from Tony Pulis temporarily in January, has also decided to release Matt Hewlett, Mark Shail and Kevin Langan, but has assured Ivan Tistimetanu and Greg Goodridge.
Taylor, who played in the top-flight for Swindon earlier in his career, and the hero of the 1994 FA Cup shock win over Liverpool, Brian Tinnion are both long-time serving Robins players, while Millen moved from Watford last summer but had an impressive year and is currently the City captain.
Former England coach David Burnside will stay at the club to look after the club`s youth academy.
"I'll be speaking to Keith, Shaun and Brian about getting them involved. I've been hugely impressed by all three's attributes," Fawthrop said.
"One of the features of the scenario when I was made manager was that we would build on the strengths we have within the club.
"All three are highly qualified UEFA coaches and I believe we can utilise what we already have.
"We have to change the whole system of this football club and given we have people specialising in these areas, isn't it commonsense to use them?"
