You may run into the following error when setting up Rollup:
This generally occurs if replication was successfully completed on one database but failed on another, and as a result you had to retry the process. To fix issues like this, disabling SQL Replication on all child cores may be necessary. Please use the following document to do that: How to disable/enable SQL Replication and remove publishers for SQL Replication
If there isn't a Publication setup on the child core's SQL server then you should be fine to move on to the next child core's SQL server and validate that it also doesn't have a Publication. If it does, then remove it with the same steps mentioned in the previous document.
Once you've finished that process run the replication utility again and this error should no longer be an issue.
The main reason you'd see an issue like this is a result of the view getting in a "bad state" in the SQL server's metadata, where the SQL server reports that the view is in use when in reality it isn't. Generally going though the process mentioned above will fix the issue and allow you to finish setting up replication.