Hi I'm Japanese man.
My name is kengo.

Can an administrator/root password be got with an exclusive server?
I want to customize all personally.

"Do I have root access to my server? Can I install my software after the server is online?"

"Yes, you will have root access to your server. You may install any software you like on the machine once we have put it online for you. Remember that any outside third party software is not supported by our technical support team. "

http://www.servermatrix.com/faq.html

In the beginning, they will assign a unique password for your machine. You can change it to whatever you want. Just that if you require their support, you would need to update your password in their Orbit support area so their technicans can access your machine to provide the necessary assistance.

Your password would be secure and exclusive for that machine. If you have more than one server, you can have different password for every one of them.