There is no relationship between Approval or Vote records to the Journal object. Thus, if a Service Request generates an email, that email is not visible except by examining the "Email" business object directly. Ideally, they'd like to look at the SR's "Activity History" and find it there as a roll-up.
1) In the AdminUI, modify the Vote, add a relationship between the Vote record and the Journal object. There already exists a relationship between the Vote record and the Journal.Email sub-object but that will not be sufficient for the later stages.
2) In the AdminUI, modify the Service Request business object, opening the formView to which you want to add Approval Vote emails. You'll have to modify the Object column, click "Journal" in the Object column as shown in the highlighted image:
3) Add a roll-up chain which goes form SR -> Approval -> ApprovalVote -> Journal. Make sure to select to show the rollup records by default: