After applying this new role to the databases I received complaints from other users: many had permission-related errors. After applying their role (again) on the database the errors were solved. My question is: does applying a new role affect other existing roles on the database?
Best answer by Jeffrey TolboomView original
When applying roles to the database in the 2018.2 there is an option to apply a single role or all the roles to the database. This can be done by selecting a role in the task or to leave that field empty. The script that will be generated will be different for each option. If you have doubts about what exactly happens during this process you can choose to write the scripts that would be executed to a file. This should give more insight in what happens in the background. This file can also be executed separately in the SQL studio.
When applying a single role to the database the existing roles should not be affected. But to be completely sure both scripts that were executed should be checked, the one where the errors occurred and the one that solved the errors. Once the scripts are compared with each other further investigation can take place about the difference in permissions.
Hope this helps!
With kind regards,
I will check the scripts to see what happens.