The Servicenow connector on Workato has generic object triggers and actions (that allows you to select the table you want from a picklist of any tables) as well as specific triggers and actions (that allows you to read/write to specific tables).
To use the generic triggers and actions on our ServiceNow connector, the connected ServiceNow user needs to have the admin role in order to access the full list of possible tables (ServiceNow objects, such as incidents), as well as the columns in that table (the fields in that ServiceNow object, such as incident ID and short description).
To use non-generic triggers and actions, the connected ServiceNow user needs to have the rest_service role, as well as the roles for whatever object he wishes to read/write to. To write to incidents, that would be itil role and possibly itil_admin role. Here's a list of the possible default roles in Servicenow and the permissions they have: http://wiki.servicenow.com/index.php?title=Base_System_Roles#gsc.tab=0
Here's a quick view of the user management screen in ServiceNow. More roles can be added to suit whatever ServiceNow tables/objects you wish to read/write to.