Thanks for your reply... but nope.

We can right click on the role name in the managment tree on the role part... but actually I need the same under "Workflow Server>>Processes>>MYPROJECT>>MYPROCESS>>roles".

If I try your solution, to clean up my server and after recreate a new role for example... I've the following error message "Role has dependancies. Cannot delete." So, while my role is referenced directly under "MYPROCESS", I can't delete it... but I've no way to unreference it.

Any idea?

I'd like to remove a role from a process too... Is there a way to do so, now, except editing the database?

There is a great article on the accessing roles programmatically using the UserRoleManager over at Pitchblack http://www.k2underground.com/blogs/pitchblack/archive/2008/04/15/k2-role-manipulation-using-the-sourcecode-security-userrolemanager-management-namespace.aspx

You should be able to delete a role using the following code. 

using SourceCode.Security.UserRoleManager.Management;
using SourceCode.Hosting.Client.BaseAPI;

......

string K2HostServer = "BLACKPEARL";

userRoleManager = new UserRoleManager();
userRoleManager.CreateConnection();
userRoleManager.Connection.Open(string.Format("Integrated=True;IsPrimaryLogin=True;Authenticate=True;EncryptedPassword=False;Host={0};Port=5555", K2HostServer));

You will need to add reference SourceCode.Security.UserRoleManager.Management.dll and SourceCode.HostClientAPI.dll.