Just something really quick to ask.

I only have 1 person at Red Rocket Station and they are assigned to guard duty, but when they are, it says that Red Rocket Station has no food with an exclamation mark.

Now I do have all my settlements connected and have several dedicated to just farming food and every other settlement is fine and I have more than enough food to go around.

Did I miss something?

Your supply lines don't provide you with food. You have to go into the workshop and go to resources / food then plant some food (Mutfruit will give you 1 others will only give you .5) then you need to assign someone the job of maintaining the food. To do this inside the workshop menu you need to point to go up to a person and choose command then go to the food (planted in the ground) and choose assign.

Your best bet is getting power as soon as possible and adding a radio beacon so you can get more than one person because your going to need 3 people one for food one for supply line and one for guarding. (Radio beacons are found under power > misc i believe)

Hope that helps! Welcome to the Fallout!

I was told/read that one of the big reasons to use supply lines is because it shares your surplus of food and water throughout your settlements? Such as why ive heard so many people using certain settlements as dedicated farms to provide food?

Whoever told you that, sadly told you the wrong information. The settlements only share what could be put into the workshop (IE: junk, weapons, clothing)

Now im anxious to get home and check the in game help guide. I swear it said somewhere in there that any "surplus" of food will be distributed amongst settlements. Because I have also heard that it wont "show" this food as actual items in the workshop inventory but rather "share the wealth" with other settlements that need it. I always thought it made sense too since 1 worker can harvest multiple crops, meaning that person can provide food for more people rather than just themselves?