I've been growing icebox size watermelon (sugar baby and its hybrid cousin tiger baby) in a 25-gallon half whiskey barrel for the past five years, and it works well in my situation. I plant my seeds indoors and transplant them very gently when they have just formed their first true leaves and daytime temperatures are reliably above 70. I've grown four or five plants in the barrel and gotten an average of two watermelons for each plant. I did try trellissing them, but as soon as I see the melons begin to form, I gently rearrange the vines so the fruit is resting on the ground or some sturdy platform. The vines still range over the trellis, which is very pretty, but eventually they climb out of the pot and extend a few feet out from it on the ground. My melons are usually around five pounds, which may be a little smaller than ones grown in the ground, but they are so sweet and clean. The planting mix I've been using is the 5-1-1 they talk about in the Container forum. It's five parts pine bark fines to one part each perlite and peat moss. My situation may not be ideal, but I can't grow melons in the ground, and this works well for my small family. Here's a photo from last July. And here's one from June, a year earlier:

I think you can plant them anytime after the Forsythia blooms in your area... at that point the ground should be workable and warm for plant growth. Spring rain should also follow to keep them watered for you. You can prune if you want to but wait to see signs of life first to know where there is good or bad wood. Pruning encourages growth in roses so it is generally considered good practice with a few exceptions. Just don't prune severely! No need to get drastic. Since you overwintered them in your garage I'd expect them to be alive to the tips but you never know. As for first time tips? Well, make sure they are well fed and planted in good soil. I'm more of an organic grower now, piling tons of compost on the soil when I plant and using a slow release fertilizer only for the first year as I wait for the compost to start releasing nutrients into the soil. After that I am done with fertilizing. Since you already planted roses before, just remember that the David Austin roses are still roses so the same rules of giving them a good growing environment apply. If you live in an area with high pressure of fungal diseases then you need to figure out how you'd like to handle it because those roses you have are not disease resistant, definitely not resistant to black spot as far as I know (based on what I have read, I have grown none of them). Also your Knock Out rose can't be 20 years old as those were released in 1999/2000, if you are sure it is a 20 year old rose bush then perhaps it is something else other than a Knock Out? Good luck and enjoy!

I've hesitated to reply because I don't know! only want to sympathize with your dilemma. At our old house growing young roses up a bit in pots was basically a failure,because of lack of light, but here at the new house I can see that it's very different: plenty of morning sun and afternoon shade. So this fall I'm thinking to pot up all new roses,but just for one season. I, too, find growing roses in pots too much work and just can't keep up. Like Kes Z, I am much more concerned about losing roses to heat and drought (I'm in Italy, about a zone 8,but my garden has a south-western exposure, so it's protected from North winter winds, but subjected to terribly brutal summer sun). Still, I've always mounded/protected baby bare-root roses planted out in fall/winter, just in case. I guess in general I'd vote to plant them out in the ground,especially the larger ones,but I think I might protect them. One way that I've done this successfully is by using pieces of styrofoam-you know, those odd-shaped pieces that are used in packaging so many things? I break these up to smaller sizes, if necessary, andmake a sort of little corral around the canes of the rose,holding the pieces in place with stones,earth,whatever. Then I fill in the top a bit with other pieces,holding these in place with sticks,teepee-style,or use wine corks. I like this way of protecting because the materials are efficient insulators, but also sterile so bacteria and fungus aren't encouraged.You'd only mount these potective teepees once the temperature really drop.If some are still very, very tiny, you could keep those few in their pots.

I believe #1 is correct. #2 looks like a strawberry. #3 could be vinca or wintercreeper. I suspect it's the latter because the stems look pretty thick.