Hi Peng Yin,
UAR requests can only be grouped and by either the Manager, or the Role Owner, not both. SAP have designed the solution in this way.
However, what I would suggest is that in your case, have the UAR review performed by the Line Manager, then if a Role is to be removed, do not remove it automatically from the user, but make the UAR review generate a Access Request to be sent to the Role Owner to review (i.e. they decide if the user should have the role removed from their account).
That is probably the only feasible way of ensuring decisions are looked at by both Line Manager and Role Owner.
Happy to hear others suggestions on this forum also.