How does 'Environment Management' work in a DevOps world?
I've never heard of an "Environment Manager."  Release Management, on the other hand, has historically been consolidated to a single person or team.  

In a DevOps model, Release Management is more of a process supported by elements from both Dev and Ops.  Organizations at high levels of "DevOps maturity" don't really have a distinct Release Management event- the act of releasing is baked into the Continuous Delivery pipeline (see "push on green" What is &quot;Push on Green&quot;?)  

It's possible the OP is also referring to Configuration Management, where environment-specific configurations are managed manually, or by tools like Puppet or Chef.  That work is traditionally an Ops-managed task, with higher-maturity orgs handling that through code.  Responsibility may be shared between Dev and Ops, or there may be a dedicated SRE team that deals with Config Management.