You can hack the process swim-lanes to be vertical in JDev version 188.8.131.52.0 but, not in 184.108.40.206.0. Here is how you do in JDev 220.127.116.11.0 :
1. Close your JDev if it is open.
2. Edit your .bpmn process.
3. Search for
"<ns5:StringFeature value="HORIZONTAL_LAYOUT" name="process-layout"/>"
4. Change the same to
"<ns5:StringFeature value="VERTICAL_LAYOUT" name="process-layout"/>"
5. Save the file and start JDev.
When you open up this process in JDev, it will initially throw an error since, your activities might be messed up (if activities were was already present), coz it will not be properly aligned with the Roles, which you may have to correct it.
Not sure, why this hack doesn't work with 18.104.22.168.0.