Specify multiple roles using the Participant API

It is not currently possible to specify multiple roles using the Participant API.

This error occurs whether you supply the roles as an array of role IDs or as a delimiter-separated string of role IDs. It occurs because the API explodes the delimiter-separated string of role IDs into an array (in _civicrm_api3_api_match_pseudoconstant), but the BAO is expecting a delimiter-separated string of role IDs, not an array. This causes several (non-fatal) error messages and leaves an invalid value (the string 'Array') in the role_id field in civicrm_event_participant.