pepperbelly You may need a bottom bracket cable guide that extends through the hole in the frame:

Specialized Bottom Bracket Cable Guide (Black) (w/ Top Cap, Bolt) - Performance Bicycle (performancebike.com)

Specialized 2013-16 Roubaix Bottom Bracket Cable Guide - Performance Bicycle (performancebike.com)

Still not sure which model year your bike is, but at least these are not parts which are so expensive that trial and error is cost-prohibitive.

Note: Not too sure about the above after read Iride01 's post #12 below.