Because of the need for audit trails, etc. it is not possible to delete Function Roles in SOLABS.
Roles that are no longer required, can either be re-used for another function (renamed with a new name representing this new function), or simply renamed to identify them as obsolete by adding information such as DO NOT USE, NO LONGER IN USE, REPLACED BY, etc.
For the latter, SOLABS also recommends add a prefix such as Z_ so they will come at the end of the alphabetical order in any listings (ex.: zzz_Role1_obsolete). This way they will all be displayed at the end in Roles lists, reducing chances where users would continue selecting these roles by mistake.
It is important to update BOTH the Name field and the Job Title field with the prefix and the obsolete identifier in order to impact all listings. For example, when using the Add Activity to Profile option within a Training Activity, the list of Function Roles comes from the Job Title of the Function Role and not the Name field of the Function Role.