This will never work as you are wanting to roam between two different vendors.
Ultimately the client makes the decision and your client will want to stick to an AP.
Aruba can help with client-match but since there is only 1 AP in this network, there isn't much.
Roaming will simply not work in this scenario.
You will need to use hardware that will support this.
Using 2 linksys E4200 routers will not work either because they are considered "thick" APs and do not share information between each other.
You will need a "controller" based (either virtual or dedicated) in order to make roaming work