Add a new SPGroup programmatically to SharePoint

Recently I have developed a web application to interact with SharePoint. Its objective was to hide the SharePoint UI to the final users in order to they can administer the site collection without any knowledge of SharePoint. Users have rights to manage users and groups but we wanted that they did not navigate through the administration pages of the site. For that reason the web application uses the API to do all the operations. At the moment the most complex operation has been the "add new group" due his poor documentation. This is the code that I have used to accomplish this operation:

//Add the group to the SPWeb web
web.SiteGroups.Add(groupName, owner, defaultuser, description);

//Associate de group to the SPWeb. Now it will display in the quick launch bar
web.AssociatedGroups.Add(web.SiteGroups[groupName);
web.Update();

//Assignment of the roles.
SPRoleAssignment assignment = new SPRoleAssignment(web.SiteGroups[groupName]); SPRoleDefinition roleApp = web.RoleDefinitions["Aprobar"]; assignment.RoleDefinitionBindings.Add(roleApp);
SPRoleDefinition roleCol = web.RoleDefinitions["Colaborar"]; assignment.RoleDefinitionBindings.Add(roleCol);