Rossi raced for the team in the final rounds of last season but settled for the reserve role after Haryanto and team mate Pascal Wehrlein brought more to the team in terms of funding and engine cost offsets.
With Haryanto now filling a reserve role, there was speculation that Rossi had left the team but his management insist this is not the case.
"Nothing has changed in relation to Alexander's role with Manor, he's still Official Reserve Driver," they told ESPN.
The Californian, who has raced in IndyCar this year - winning the Indy 500, was set to replace Haryanto as it was understood he had first refusal on any vacant race seat in the team. However, he opted to remain on the sidelines owing to his IndyCar commitments and Esteban Ocon stepped in instead.
Bahrain International Circuit - Winter testing