What is roaches up on the back mean?

[Heiferplease]

Have a calf that judges say “roaches up on his back” what does that mean and what will fix it. He is also has very straight back legs and up on his toes. Help!! Will more exercise lest high protein feed help?

 

[knabe]

Rounds up in the back. Some have said selenium supplement shots will loosen pasterns.

Best not to choose either when picking out cattle.