Hi,
Select the related label group, click right, select Edit Band Style. Then click on Compose Label (the one on the right side) In Layout tab, change the Rotation Angle to 90 degrees.
You must do this at each place though (like at major increment , at centerline,at sample line vertices etc. ), depending on the way you 've created the label set.
Erdem Çelenk
Civil Engineer,MSc.