Here is a link to a blog that has easy jelly roll patterns.
https://www.craftsy.com/blog/2015/04...uilt-patterns/
The patterns appear to be free but it looks like you have to add them to your cart to get them.
There are many free patterns and tutes on the web. I would recommend using pinterest or Google Images and search for jelly roll quilts. Many are block based so you could Quilt as you go or a "fun and done" type method.
Here is a pinterest search I just did
https://www.pinterest.com/search/pin...yped&term_meta[]=Jelly%7Ctyped&term_meta[]=roll%7Ctyped&term_meta[]=quilts%7Ctyped
However, I think you will need to add at least another Jelly Roll (perhaps a solid white or cream). 2 rolls only give you not quite 6 yards of fabric (less than two meters). The average king size quilt will take anywhere from 9 to 12 yards (3 to 4 meters) depending on pattern and no telling how much waste you will get using jellyrolls. And I am not sure that yardage estimate includes backing. I just did a quick search. I make mostly queen size quilts and, on average, I use 7+ yards just for the top.