That’s why it’s always recommended to do research before a purchase, not after.

”Note that Line-In is disabled when Fives or Play:5s are being used as surround speakers in a Sonos home theater.”

https://support.sonos.com/s/article/4837?language=en_US

If you want to add a CD player to your Sonos setup, you could always get another Five or a Port:

https://support.sonos.com/s/article/1080?language=en_US

Another option is to rip your CD collection to your computer or a NAS and connect the Sonos app to your digital music library:

https://support.sonos.com/s/article/257?language=en_US

That’s bull, dude I had to dig deep to find out that the line in would be disabled if chosen as surrounds. Sonos shouldn’t be hiding limitations on a support page, something like this should explained on there home theater and product page. Anyways I feel like I’m missing out by not having an AVR setup so maybe I’ll put the Sonos in the bedroom. Thanks anyway.

Can you name another company which prominently lists limitations on their product pages? 

Amazon does actually.  You will often see a ‘We want you to know’ section on Amazon products that discusses limitations.  I’m not suggesting that Sonos do the same, but stating limitations that will be commonly run into in the FAQ section seems valid.  And Sonos does this actually do this.  In the Five’s FAQ, you can learn that you shouldn’t connect to a TV, use outside, and can’t use on an S1 system.  It mentions that you can use the line in, and can be used as surrounds, but does not mention that you can’t use the line in when setup as surrounds.  Seems like this is a common enough question/assumption to mention in the FAQ without sounding too negative.

I agree with @melvimbe the answer about the Five line-in being disabled when used as surrounds should be addressed in the FAQ’s.  Using the “search” icon is probably the fastest way to find the answer but even that requires two (2) clicks as long as you know the keyword to type (i.e. Line).  I don’t see any negative to mentioning it in the FAQ’s as it’s the design of the speaker for a a good reason (i.e. speakers used as surrounds cease to be autonomous). So...IMO the OP has a point...but as @GuitarSuperstar mentioned “research’ before you buy...when possible.