Problem

The jira.permission.assignable.projectrole restricts the assignees to users associated to project roles.

Currently, it will only take effect if added in statuses. The issue view will be affected in the current status, and all the transitions that go out of that status as well.

But, in some cases, there may be different transitions coming out of the status, but you do not want to restrict the assignee on both of them, or at least the same way.

Suggestion

Have that property work when applied to a transition, so it is possible to restrict only at project level.