"Rolls are a science unto themselves." X 2 The fungibility aspect of the contract and the variables introduced by the various delivery scenarios. It is, literally, a large game into and unto itself. And it gets gamed and squeezed when the opportunity presents itself.
Yup, especially rolls in US bond futures where there is a fair bit of CTD optionality. There are a lot of things to do around basis, rolls etc if you know what to do. For a retail person (e.g. someone with P&L target in hundreeds of K, not in millions per year), there is also a lot of fun stuff to look in trading futures vs ETFs.