Server Manager has a very rudimentary help facility. To use it, just type in HELP at the prompt.
This is an example:

SVRMGR> HELP

In return, you will see a brief summary of command syntax. You won't see a lot of detail--for that you will have to go to the manual, but often a reminder is all that you need. Try the following simulation to see how the HELP command works.

Use Of Roles
Using roles has several benefits, including:

1. Reducing the number of grants and thereby making it easier to manage security.
2. Dynamically changing the privileges for many users with a single grant or revoke.
3. Selectively enabling or disabling depending on the application.

Roles can be used for most system and object privileges. Privileges granted through a role cannot be used for creating an object (views, packages, procedures, and functions). You need to grant privileges directly to the user for this.
Oracle HELP Command