Hi Partner,
Maybe you can use Security Role Merge tool from XrmToolBox to merge two security roles.
Security Role Merge · XrmToolBox
For example, i want to merge following two security roles:

(1) Download XRM ToolBox. https://www.xrmtoolbox.com/
(2) Once you have downloaded and installed it, then connect to you crm environment.
Insert organization url and password, you can connect successfully.

(3) Go library to install Security Role Merge.
(4)Open it and do following operations:

Result:
The third new security role can be created with permission from Test1 and Test2.

Regards,
Leah Ju
Please mark as verified if the answer is helpful. Welcome to join hot discussions in Dynamics 365 Forums.