In Salesforce orgs created in Spring ’21 or later, you can create up to 5,000 roles. In existing orgs, the default limit hasn’t changed. You can create up to 500 roles and can contact Salesforce Customer Support to increase this limit. Keep in mind that to improve performance, it’s best to set up roles based on data access and eliminate any roles that aren’t needed.

Where: This change applies to Lightning Experience and Salesforce Classic in Professional, Enterprise, Performance, Unlimited, and Developer editions.

https://help.salesforce.com/s/articleView?id=release-notes.rn_forcecom_sharing_roles.htm&release=230&type=5

With manual sharing in Lightning Experience, you now can share records and manage record shares in a new streamlined interface. Previously, you switched to Salesforce Classic to give specific users and user groups access to records.

Where: This change applies to Lightning Experience in Professional, Enterprise, Performance, Unlimited, and Developer editions.

When: This functionality is available on a rolling basis starting in the Spring ’21 release and is available to all customers by February 27, 2021.

Why: Click Sharing on the record that you want to share. In the Share window, you can manage who the record is shared with and share any associated records. Manual shares are available only for accounts, opportunities, cases, contacts, leads, and custom objects.

https://help.salesforce.com/s/articleView?id=release-notes.rn_forcecom_manual_sharing_lex.htm&release=230&type=5

We made changes to the Read Only profile that you’ll want to know about. And, we now have integration permission sets.

• Convert the Read Only Standard Profile to a Custom Profile (Update)
  This update converts the Read Only standard profile to a custom profile. After the update is enforced, you can edit permissions in this profile as your business needs require.
• The Read Only Profile Is No Longer Available in New Salesforce Orgs
  Salesforce orgs created in Spring ’21 and later don’t have the Read Only standard profile. If you want to assign users read-only permissions, we recommend that you start with the Minimum Access standard profile as a least-privilege profile base. Then you can assign custom permission sets to grant users the read access required for your business needs.
• Use Integration Permission Sets to Exchange Data with Integration Partners
  Integration permission sets define the scope of data access by Salesforce integration-related features and services. Depending on the integration features, Salesforce can predefine the integration permission sets so that they aren’t editable in your Salesforce org. Or, an integration permission set can have no initial permissions so that you have full control for your org. An integration permission set can also come with on-premises permissions that you can modify for your org.

https://help.salesforce.com/s/articleView?id=release-notes.rn_forcecom_profiles_perms.htm&release=230&type=5