These can be sown directly into the raised beds- Sow very thinly in very shallow lines and just pick / thin them out as they grow:
Rocket
Radish and beetroot - for the leaves
Carrots
Anything from the cabbage family (kale, sprouts, broccoli, etc) - better to go in the centre of the bed and let them grow on. You can pick leaves etc as you need them / before they yellow and drop off at the bottom. You could start them off in standard plant pots so you give them a hgead start before transplanting them, and that way you won't grow too many at once, either.