Matt, I really appreciate that you contribute so much. I think it's really helpful when people read your posts.
I have always told people they would be surprised by the many side effects of having a balanced strength training program, not the least of which is better flexibility. It usually surprises people but if you are contracting your muscles in a methodical manner then you are also teaching the agonistic muscles to perform better in their participation of the motion. The body is always working in an agonist/antagonist relationship. If you are doing a chest press then the rhomboids and other back muscles must hold appropriately to supply a stable foundation so you can access all the strength of the chest muscle. If your participating muscles can't allow for proper flex and resistance then you dilute the ability of the chest to perform. It is in the weight room that you have an opportunity to fine tune these relationships.
The roller Matt mentioned can be purchased on any golf equipment site. It is a hard foam cylinder, typically 36" x 3" and shouldn't cost more than about $10. A number of exercises can be done on them but one of the best is just to lay down on it from the base of your spine with your head at the top. Stretch your legs out long and let your arms hang off to the side. Lay here for 5 minutes. Roll off the roller and lay on the floor for a few minutes. Yes folks, this is called passive exercise but it is very effective. My private clients laughingly call it 'the beloved'. This posture allows you to open your ribcage laterally and the effects can be profound. You can also get a half cylinder but I like the full roller for balance and versitility.