When syncing your Google Classroom results into Gradebook, you'll see an "Update All" button when there are updates in Classroom that aren't yet reflected in Schoolrunner's Gradebook. It also indicates how many assessments will be updated.
This button will update all assessments that have been previously synced in from Google Classroom (including any that don't count for grades) but it will not import new Classroom assessments that aren't already represented in Schoolrunner. In other words, you still have to import new Classroom assessments individually into Schoolrunner, but after that's done you'll be able to bulk update results with this button. This button only appears when there are new results in Classroom for assessments already in Schoolrunner.