CREATE ROLE prodavec;

ORA-65096: invalid common user or role name
65096. 00000 -  "invalid common user or role name"
*Cause:    An attempt was made to create a common user or role with a name
           that was not valid for common users or roles. In addition to the
           usual rules for user and role names, common user and role names
           must consist only of ASCII characters, and must contain the prefix
           specified in common_user_prefix parameter.
*Action:   Specify a valid common user or role name.