The Premier League champions are keen to bolster their squad with the acquisition of Mahrez this summer but Leicester are proving a difficult party to negotiate with.
Reports in England suggest that the 'Foxes' will only consider selling one of their star players, if the young Roberts is included in a part-exchange.
The 21-year-old has allegedly been on Leicester's radar for some time after impressing during a two-year loan spell with Celtic.
It is unclear whether City would be happy to include Roberts in a potential deal, or whether they would rather negotiate the two transfers separately.
Mahrez is valued at £60million, although the inclusion of Roberts could push that price down to around £45m.