I am creating a custom component for signing up and creating a website on the fly... however the website that has the sign up form is at the root level.. and my JMS is installed on a subdomain.

IS it possible to call the multisite component and create a site by passing it the variables needed (site id, template, domain, etc)... beings the multisite component is not installed on my main domain.

Example: my main domain: sherdog.com - this domain has a separate joomla installtion and does not have JMS installed

My Master site domain is : master.sherdog.com - This domain has JMS installed.. and I can create sites using the multisites component currently.

I need to be able to connect my sign up component on my main domain sherdog.com to the JMS that's installed on master.sherdog.com

I just need to know if it's possible.

The sign up form.. has the required information to create the new site (site id, template, domain, etc)

Ok.. Well maybe you can direct me to where to find the class/function something that actually creates the new site? I would assume it would be a since function that take the required information (Site id, preix, template) to which it creates the site structure.

If you want to create websites from the front-end, you have to install JMS and use it facility to directly create websites from the front-end.
If you want to change the front-end layout, this is also possible.

See for example our www.mywebsites2win.com website that is developement.
It allows creating any kind of websites based on "website ready to use".