Confused about crop rotation

Hi there, I am just starting out in veg gardening, OH and I have constructed a four raised bed potager but now I am getting confused about what to plant in which, we are going to do a four year crop rotation which I understand having read up on it, but I have just started to try and plan what goes where and found that although potatoes are in the same family as tomatoes I can't plant them together and the same with carrot and parsnips???

The plants we have grown in the greenhouse so far are as follows:

Peas
Broad Beans
Runner Beans
Tomatoes
Aubergine
romanesco broccoli
Cabbage
Broccoli
Asparagus Peas
Peppers
Chillies
Swiss Chard
Cucumber

We also are planning to put in:
potatoes, radish, carrots, parsnips, spring onions and some salad leaves plus some herbs and some marigold and nasturtium

We have already planted some of the peas and beans in a seperate bed but wanted to put some in as centre pieces in obelisks in a couple of the beds

HELP!!!

 

Have a look in here http://tinyurl.com/ytwqf9 it might help.

 

Thanks will have a read