Hi Stillnoid....baskets sound lovely...as for whether the plants will go together...when it comes to baskets..it's all a matter of taste isn't it! You go with whatever you find beautiful...there's always someone who will disagree! ;0 Take courage :) Sorry, I'm not familiar with your rose selections, but if they are climbers that like sun and you prepare the ground well and keep them well fed and watered...again, it's your choice....just check the ultimate height isn't too tall for the spot you're putting them in ...that's what I forget to do all the time! :) Oh, and if you need to walk past them alot (if they are on the door side of the shed or a narrow passage, it might be worth considering how thorny they are..you don't want to be catching your clothes on them). Enjoy your garden! :) Karen

I am all for trying it and see! But I find the Petunias will block out other annuals such as Pansies and Nemesia if mixed in baskets. You might like the results more if you grow them in separate baskets? I personally find that pansies are great for winter/spring baskets but I am not so keen in summer baskets.
One idea/theme for summer bedding this year is red, white and blue due to the Jubilee and the Olympics! I plan to have red, white and blue baskets of Petunias this year.
Dont forget to add water retaining gel/tabs quite low in the compost as this really does help them.

Baskets in your porch will be fine, but what you plant in them might be influenced by how much sunlight they get in that situation. Pansies are fine in shade, petunias not so much.
As for the choice of climbing rose, what you need to consider is the height and spread of any you like the look of - White Cockade, for instance, is well suited to growing up a pillar or arbour, and is a short grower compared to some, reaching about 6 or 7 feet. Pink Heidelberg and Etoille de Holland make 12 feet, and the latter is suitable for a large wall, say on the side of a house, so may be a little big for your purposes on your shed. Golden climber appears to make 12 feet, but I can't find any other info about it in terms of spread.