You don't need rotateX in your declaration, transform: rotate(42deg) will work just fine.
Note you will also want to include browser specific variants:
-ms-transform: rotate(42deg); /* IE 9 */
-webkit-transform: rotate(42deg); /* Chrome, Safari, Opera */
transform: rotate(42deg);
You can do this via set style, or inline via the index.html like so:
<style> input { transform: rotate(42deg);}</style>
Alternatively you can use an external stylesheet - with these two methods you'll have to pay attention to specificity if you want to target singular inputs.