yes, that css looks correct. IT is specifically targeting only the one field with the ID sprytextfield1, you could use the input selector to broaden the rule and apply it to all input elements:
input {
border-radius:6px;
-moz-border-radius:6px;
-webkit-border-radius:6px;
}
The css should go in your main css file, not the spry css file.
see the following page for more details on styling form elements:
roadmap_03.php