Start with picking one of those dimension to check the style it uses. The Command bar wil display this:
Open the Style dialog from the ribbon bar:
In the Style dialog, select 'Dimension' in the Style type list, then from the Styles list below it, pick the dimension style you noted from the Command bar in the previous step, then Modify...
In the 'Modify Dimension Syle' dialog that pops up, take the Text tab and change the Orientation to Vertical:
Ideally, you should create a new dimension style just for this case, since other dimensions in the sheet using the same style can be affected.
The screenshots are from ST6 and I believe there are some direct methods of changing the orientation using handles in ST9.