Here's my soapbox on wireless roaming.
Just because you can set up multiple APs in a given area running the same SSID does not mean that you won't have roaming issues. The AP system has to have intelligence where each AP is aware of the other. What this means is the system will automatically select non overlapping channels for each AP so no one AP that is adjacent to another will be operating on the same channel; thereby preventing co-channel interference. A wireless system of this type will constantly monitor the surrounding RF space and make any necessary adjustment to the operating channels to keep the network from dealing with interference from neighboring RF sources. The below picture is showing an example of a 5 GHz deployment where co-channel interference is being managed:
The other thing the system will do is to adjust power output so no one AP is over powering another. This is counter intuitive to most lay people as they think an AP cranked all the way up to what it can output RF wise is best. No. This is not the case. It will cause roaming issues as the client device will start bouncing between APs. This picture is a predicted heat map of a wireless deployment I did for a non profit. Notice the red areas do not overlap which is where the signal from the APs are at its most intense.
The last part of a unified system is the ability for the wireless system to do band steering and to force the client to associate with the AP which has the best QoS available. Roaming algorithms for client devices are not that great and they also suffer from AP "stickiness" where the client will stay associated with the initial AP even as you walk away from it and signal strength is weak.