Roles can be set on bot level. This means that you need to add users to specific bots. User can have different roles per bot.
Add user to bot
Go to the bots in the admin panel -> bots tab. Select the bot you want to add users too. The users have to already exist in your tenant. Select which role you want to give your users and Save your changes. Roles can be configured in the roles tab.
Tenant Admin
A user can be flagged as tenant Admin, this is the highest level of administrator rights and this user will have access to all bots in the tenant.