In jBPM5, use a rule task and give your set of rules a name (i.e. ruleflow groupattribute).
Next, use Drools to define your rules and add these rules to the group you selected (using ruleflow-group attribute).
Your rules should now be executed when you reach that node.
Example can be found here:
https://github.com/krisv/jbpm/blob/master/jbpm-bpmn2/src/test/resources/BPMN2-RuleTask.bpmn2
https://github.com/krisv/jbpm/blob/master/jbpm-bpmn2/src/test/resources/BPMN2-RuleTask.drl
https://github.com/krisv/jbpm/blob/master/jbpm-bpmn2/src/test/java/org/jbpm/bpmn2/SimpleBPMNProcessTest.java (method testRuleTask())
Kris