Redmine

Iт my project I need all New Issues to be assigned to Users with one role (fore Example role-1), but this issues can be created by users with two other roles (role-2 & role-3).
Checkbox "Issues can be assigned to users with this role" activated only for role-1. Role-2 & role-3 have no such option activated (I need them to be able to create new Issues, but not to be assigned for). But Users with role-2 & role-3, creating a new Issue can choose whom to assign for it from the list of users who has role-1, himself or the same role as User (role-2 or role-3). How can I limit list of users, who can be assigned for new Issue by only one role (role-1)?