In Alarm Definitions, Initial Alarm Owner, can this be assigned to a Role or just a single user?

The field takes a user, not a role..

https://doc.milestonesys.com/latest/en-US/standard_features/sf_mc/sf_ui/mc_alarmdefinitions_alarms.htm?cshid=9541

As this does not pertain to development but to a general situation you will most likely get better help from the partners active in the Support Community - If my answer is not fulfilling please ask at - https://supportcommunity.milestonesys.com