PDF/UA compliance - Actual text for tag

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:
```

(I)
(II)
(III)
(IV)
(V)




Content
Content
Content
Content
Content

```
What I need to achieve: