How to assign IDs to each radio button in drupal form radios?
You need to use theme_radios() hook in your template.php file, if what you get is insufficient.

Parameters
$variables: An associative array containing:

element: An associative array containing the properties of the element. Properties used: #title, #value, #options, #description, #required, #attributes, #children.

Return value
A themed HTML string representing the radio button set.

To interfere with single radio element, see theme_radio(), of course.