Hanami is not a micro-framework, it is composed of multiple gems though, so if you remove them all you're left with a core of the framework that doesn't do anything except providing an API for plugging in components, configuring them and managing their state.
When it comes to differences - Sinatra is not as feature rich and it's got a less powerful plugin system. Roda has a completely different router using so called Routing Tree, which Hanami doesn't have (it's got something more akin to what Rails has) but it's also highly extendible through plugins, so there is similarity there. A huge difference is that Hanami ships with a very powerful code loading system that supports automatic dependency injection mechanism.
When it comes to differences - Sinatra is not as feature rich and it's got a less powerful plugin system. Roda has a completely different router using so called Routing Tree, which Hanami doesn't have (it's got something more akin to what Rails has) but it's also highly extendible through plugins, so there is similarity there. A huge difference is that Hanami ships with a very powerful code loading system that supports automatic dependency injection mechanism.