I am using the toolset access plug-in to create a custom role called Research Investigator Profile Editors. I set the permission settings so they could only edit the custom post type Research Investigators. The custom post type has the field for a featured image. For the custom role user they don't see the option for featured image when creating a new research investigator. However, if they are editing an already existing research investigator that has a featured image already uploaded, than they can edit the image and switch it out for a new one. Is there a way to have the custom role upload a featured image?
Is there any documentation that you are following?
No.
What you need to do is - navigate to:
=> Toolset => Access Control => Toolset Forms tab => "Post Forms Frontend Access" section grand the permission to your desired role under the column "Use any Media Library file when adding files to front-end Post Forms".