Debbie, although you only posed one real question about how I manage to incorporate and maintain yummy meals during winter when “fresh” items are scarce or really expensive, I also see that you asked about vegetarian proteins.
I will start with the protein and give you a list of possible vegetarian protein sources which include tofu (here's my Tofu Italiano), tempeh (not well loved by many non-vegetarians but can work crumbled in foods), seitan, which is wheat gluten and all about the texture, not the taste because it has very little, if any, and beans. Then there are, of course, all the other legumes which include peas, split peas and lentils. There is obviously a large number of food items to choose from. You can also include nuts and seeds as a complement but not as the main protein source as they have a lot of fat.
If you like grains, you can cook some possibly new-to-you grains such as quinoa and then combine them with seasonings (or herbs) and beans in the food processor and turn them into burgers. I brush mine with oil and bake them until done.
Now, on to your question about the winter and vegetables. You are correct that there are fewer vegetables in winter, which is why it’s great that you asked this question now. Summer’s abundance is a great time to stock up for winter. For most vegetables such as broccoli, cauliflower, green beans or peas, blanching the vegetables (giving them a quick dunk in boiling water) and then patting them dry, and packing them in usable amounts in freezer bags works great. You can also freeze the on cookie sheets so that the vegetables are individual and freeze them in the bags. You can then pull out what you need.
Even though I live in Northern California, which is close to a winter vegetable paradise, I rely on a lot of root crops and cabbage then. It’s what you are supposed to eat, according to nature. The cooking is about learning how to be creative with rutabaga, sweet potatoes, celery root, turnips, potatoes, and how to combine them with seasonings in unique ways that make them taste great.
My friend Katie, who lives on the Upper Peninsula in Michigan, has a greenhouse and manages to keep kale going in there all winter. I suspect that you may have local or semi-local farmers who have managed to do the same. Kale, collards and Swiss chard often can make it in the mild parts of winter, if there are any.
BTW, you can tell that I don’t think that there’s anything wrong with frozen vegetables. I buy as much in season as I can but there are times when that becomes far too challenging and that’s when I turn to my freezer or use my canned tomatoes.
Here’s how I describe the seasons: Winter is roots, spring is shoots and summer and early fall are fruits. Greens exist all year in various forms. Eating food that’s local and in-season helps us attune to the local climate and generally what our bodies need.
What kind of questions do you have about products? I didn't mention any "fake meat" products and sometimes these make for a helpful transition from meat eating.