How can I set policies for an API role?

It doesnt appear you can use the UI to do this. The only thing available in the UI are the default policies.

However, you can approach this 1 of 2 ways, which youve kind of laid out above, you can re-create the role via API with the specific API policies as you see with what is similar to the user role.

i.e:

curl -X POST "http://IP:9000/api/v1/system/roles" -H "accept: application/json" -H "Authorization: Bearer TOKEN" -H "Content-Type: application/json" -d "{\"id\":\"api_user\",\"policy\":[\"GET /master/groups\",\"GET /system/info\",\"GET /system/info/*\",\"GET /system/logs\",\"GET /system/logs/search\",\"GET /system/logs/notifications.log\",\"GET /system/logs/group/${groupName}/*\",\"GET /system/settings\",\"GET /system/settings/*\",\"GET /system/instance/distributed\",\"GET /system/instance/distributed/*\",\"GET /version\"]}"

However, if you already have the role created, you can then use the API to create a new policy and just apply it to that role:

i.e

curl -X POST "http://IP:9000/api/v1/system/policies" -H "accept: application/json" -H "Authorization: Bearer TOKEN" -H "Content-Type: application/json" -d "{\"id\":\"api_policy\",\"template\":[\"GET /master/groups\",\"GET /system/info\",\"GET /system/info/*\",\"GET /system/logs\",\"GET /system/logs/search\",\"GET /system/logs/notifications.log\",\"GET /system/logs/group/${groupName}/*\",\"GET /system/settings\",\"GET /system/settings/*\",\"GET /system/instance/distributed\",\"GET /system/instance/distributed/*\",\"GET /version\"]}"

Something like above will create a policy with the specific attributes that you need and then you can assign it to the existing role.