Perhaps put custom roles in a DB table where you store the roles and tenant, and then PagePermissions in another table, for example:
Table "Role"
RoleId, TenantId, Role
Table "PagePermissions"
PageId, RoleId
Table "UserRoles"
UserId, RoleId
, RoleId, , :
Select PageId FROM
UserRoles UR INNER JOIN PagePermissions PP
ON UR.RoleId = PP.RoleID
WHERE UR.Userid = @UserId AND PP.PageID = @PageId
, .