When I upgraded Sitecore version from 9 to 10, the users and roles were required to be migrated. In this case, I follow the next steps to accomplish that.
First, I created a package with the users and roles using the Package Designer utility inside the Sitecore source CMS. For that, you have to click on “Security accounts” menu option, and it is shown the following screens to add the roles and users to be migrated. After this selection, the Sitecore package can be generated and download.
Second, import the package with users and roles to the target Sitecore CMS instance.
Next, Sitecore provides in this link the TransferUserPassword page to migrate the password data. It is required to download it and copy inside the sitecore\admin solution folder. You have to access to this url:
<hostname>/sitecore/admin/TransferUserPasswords.aspx
It is displayed the following screen to set the source and target core connection strings. Search the users and transfer between the Sitecore databases with the buttons <<< and >>>
Finally, access to the “User Manager” option in the target CMS to check the users migrated. In case that users are disabled proceed to enable them.
That is what you need to do to migrate users and roles between two Sitecore instances.