The current UK immigration permission system for both full-time and part-time long term study in the UK is the Student Route Visa. This is the type of immigration permission the majority of international (including EU/EEA nationals) students will require to study at the University of Roehampton.
The Student Route was first introduced in October 2020 but older Tier 4 visas are still valid forms of immigration document, so you can remain in the UK legally if you still hold the older visa type.
Detailed guidance for this visa type can be found here: Immigration Rules: Appendix Student - Immigration Rules - Guidance - GOV.UK (www.gov.uk)
General information on student immigration and how the Student Route fits into the UK immigration framework can be found here: UKCISA - international student advice and guidance - Student immigration: the basics