Giving ants only one food source is pretty much a recipe for malnutrition. There may be ants that are so specialized that they only eat one food item but most ants are not. This doesn't necessarily mean that they will suffer from malnutrition when always given the same food but the risk is extremely high.
I could possibly give them 2 protein sources, mealworms and crickets I will make myself handle, not roaches though. I will stick with the two honey and sugar water sources and I will feed them at least 2-3 different types of seeds. Is that enough to prevent malnutrition?
Most of what I've researched has been targeted at feeding fish or reptiles because I've kept them for more than 35 years and have been making and developing homemade frozen foods for them for nearly that long, I'm new to ant keeping so I don't know that I can offer very much relevant information but I can offer a few insights.
If you look at charts detailing the composition of various feeder insects you'll see that they can be quite different, not in so much that they contain different proteins, vitamins and minerals but more in that the ratios are different which can effect the uptake of certain vitamins and minerals, therefore it is best to use a variety if possible.
As stated above a variety of foods will lessen the chance of malnutrition because where one food might be deficient in a nutritional element another food might provide it in abundance, offering a wide variety of foods is the best way to make sure there are no 'gaps' in the nutrition provided.
As for providing different protein sources I think you don't realise how many are available to you just from day to day life. If you have other pets their food can be offered, fish food, cat food and dog food all provide different forms and ratios of proteins and can be added for variety.
I would also hope that in your household most days there would be some type of fresh meat used in preparing food for the family, small pieces can be put aside for the ants providing them with for instance beef one day, chicken another day, fish another day and so on (apologies to vegans/vegetarians). There are also vegetable sources of protein as vegans/vegetarians well know, nuts, grains, legumes and mushrooms spring to mind.
Then of course why not provide some of the vegetable and fruit scraps that result from food preparation, lots of variety there too. Of course these can also be fed to feeder insects to vary their nutritional value, gutloading is a very common practice in lots of animal husbandry and should really be as simple as feeding the feeder insects an hour or so before using as food, vary what you feed the feeders and you vary the nutrients they provide to your pets.
I can't see where you should be limited to mealworms at all, there's so many other options just in your house I would suspect! I do see where it is useful to have a staple protein source such as mealworms, they are certainly the easiest feeder insects to keep and breed. Feeding mealworms a slightly different mix of vegetables each time before feeding them to your ants will mean that they will provide the most range of nutrients possible.
