To add a new minor version of an application ruleset for a phased rollout, you would lock the current version of the ruleset to prevent further changes (this is referred to as "rolling" the ruleset), and then create a new minor version. The application record should be updated to reference this new minor version of the ruleset.
This ensures that the new features can be tested and gradually released to the user base without the need to create a completely new application version. References: Pega Senior System Architect documentation on versioning and release practices.