PDF/UA compliance - Actual text for tag

[Igor-Berendejev]

I have a HTML template that contains a table. The table header contains only numeration of columns with roman numbers. To achieve the accessibility of PDF generated from this HTML template I need tag to have Actual Text property.
How can this be achieved? Either programmatically or via improvement of HTML?
Here is HTML code snippet:

<table>
  <thead>
	<tr>
		<th scope="col" aria-label="Actual text column 1">(I)</th>
		<th scope="col" aria-label="Actual text column 2">(II)</th>
		<th scope="col" aria-label="Actual text column 3">(III)</th>
		<th scope="col" aria-label="Actual text column 4">(IV)</th>
		<th scope="col" aria-label="Actual text column 5">(V)</th>
	</tr>
  </thead>
  <tbody>
	<tr>
		<td>Content</td>
		<td>Content</td>
		<td>Content</td>
		<td>Content</td>
		<td>Content</td>
	</tr>
  </tbody>
</table>

What I need to achieve: