It sounds like you might not have the right permissions to change that person's role. Note that you also can't downgrade the role of someone who has the same role as you.
For example, if you are an organization manager and you change Susan's role to organization manager, you will no longer be able to go back in and change her role back to organization member. To do this, you'll need to ask the account owner to do this for you.
This means that the project has already been assigned to the team. You can continue to assign the project, but the permission level you set will override the one that is currently set.
Unfortunately, we do not keep that information once you have deleted it, so we are not able to restore a deleted project. We suggest revising permissions on your account to limit who can delete projects in the future.