While android has some settings as far as disabling roaming completely, I would simply like to disable only calls (due to their expensive nature), and allow MMS/data via roaming - is there any way to do this?
You can block the calls, but I dont know if there's a way to disable them.
Avast has one such built in tool to block calls by pattern i.e. wildcard characters. e.g. block all calls with +1800* ( i.e. block all calls starting with +1800)