No you can’t. You will need to use Preview and Beta: Amazon Echo Control to create things from amazon into openHab
This is quite good as some devices don’t have a native openHab binding and this way can be controlled by OH. BUT not the other way around. The amazon polling period is 10 minutes so don’t expect live updates of items controlled only via amazon. For example I have two “smart” wall socket for which exists an app and an alexa skill. Via the amazon echo control binding, I can turn them on or off but If I turn them on/off manually I have to wait up to 10 minutes to see the update in OH. Nevertheless it is quite exciting because devices like the Nest thermostat from which google (In their great wisdom) stopped the public API will be controllable via this binding with the amazon echo acting like a bridge.
On the other hand, MOST items created in openHAB can be controlled, viewed with alexa by using: openHAB Skill For Amazon Alexa | openHAB
A raspberry pi is the perfect entry level single board computer that you need