Create a Custom Role
Specific permissions are required for the Google Cloud Storage Connector to access buckets. This set of permissions is the combination of the permissions associated with the existing Google Cloud IAM Role called "Storage Object Admin" and the Google Cloud IAM Permission called "storage.buckets.get".
Steps
In the Google Cloud Platform web console, navigate to IAM & admin > Roles
Click on +Create Role.
Provide the following:
Enter some title under Title
Enter some ID under ID
Under Role launch stage select "General Availability"
Click on Add Permissions and add the following permissions:
storage.bucket.get
storage.objects.create
storage.objects.delete
storage.objects.get
storage.objects.getIamPolicy
storage.objects.list
storage.objects.setIamPolicy
storage.objects.update
Once done adding permissions, click on Create.
After performing these steps, a new role will be created.