It's different with each college/training centre hence the ambiguity when searching for a defining job role. I'm a RDN and NVQ Assessor and my job role is to 'deliver the course to meet City And Guilds requirements' read that how you will.
Basically I ensure that my candidate meets all criteria laid out in the C&G standards via observation and action plans.
Some colleges will expect you to deliver training - colleges don't call it teaching anymore, but you may be expected to complete a course in delivery
Hope this helps x