Help Backup ROM

[Soapm]

I want to try a few custom ROM's just to see if I can get spell check working on my Galaxy Tab S 8.4.

Is there a way to back up an image of my current ROM, try a few custom ROM's and restore my device to exactly how it is now if I don't like the custom ROM's?

I have plenty of space on my Linux video server to store the image, I need to know how to go about this or what key words to search for?