Routis has penned a two-year contract at Scottish Premier League side Ross County, while Sheehan will join Sky Bet League 2 Luton Town on a permanent basis having played for the Hatters on loan earlier this season.
Like Routis, Sheehan has also signed a two-year deal with his new club.
Following his move to Victoria Park, Routis will join up with former City team-mate Andrew Davies, who helped Ross County to win the Scottish League Cup after signing for the Staggies last season.
Routis made 38 appearances in total for City over two seasons after moving to the Bantams on the eve of the 2014/2015 campaign.
The Frenchman, who played in both midfield and defence for City, also netted three times.
Speaking about his departure from City via his official Twitter account, Routis said: "I would like to thank Bradford, all the staff and the players, for two fantastic years.
"There is no way to describe the fans - they are one of the best set of supporters in the country, certainly League One.
"It is now time for a new start for me and an exciting new challenge. Thank you for everything."
Sheehan leaves the Bantams having played 32 times for City over the course of two seasons. The Irish defender spent most of the 2015/2016 campaign on loan at Notts County and Luton.