Checked Definition of Roles as well as Definitions of States and Properties of W3C's Accessible Rich Internet Applications (WAI-ARIA) spec, but there doesn't seem to be any roles or states defined for file picker (or file uploader in general). Are there any at all? And how required they are in such case?
If you are using an <input type="file" /> you do not need to add any ARIA roles to it, as what is needed is already built-in natively. If you ran the W3C validator and it threw something about missing some aria-related attribute, simply ignore it for now. The validator was updated a week or two ago and some bugs were accidently thrown in.