Using a bike pannier as a shopping trolley: the B&W International B3 Bike Bag.

Normal pannier bags are great on a bike or trike, but they do have one major disadvantage.  Once they leave the bike you will need to carry up to two panniers using a thin strap that cuts off the circulation in your fingers. Cyclists' rooms in the five star hotel de luxe or youth hostel are always a long way away from the entrance up two or three flights of stairs in another time zone and by the time you get to the room you have numb hands and claw-like fingers. I realise that one can attach a carrying strap and sling them over the shoulder, but the panniers get mucky and wet. Carrying them then can lead to domestic strife. We once went by bicycle to the Mannheimer Maimarkt (a regional Ideal Home/travel/DIY/agricultural show). I carried a pannier bag over my shoulder in the halls to transport  pamphlets and anything else we could scrounge. When we returned to the bikes I realised that the inner, wheel-side of the bag was very dirty. The panniers were used several times a week and had picked up greasy road dirt. This had transferred to my shirt. I was not a happy camper. I was not popular with her indoors either. 
I am impressed with the B&W International B3 Bag. This is a pannier bag equipped with two wheels and a telescopic handle. It would solve the hotel/hostel baggage problem when touring. We would probably use it primarily as a shopping trolley. It can be filled in the supermarket and then attached directly to the bike/trike.  It weighs about 4lb for a closed volume of 35L. This is about 1lb heavier than two Ortlieb Backroller Bags (40L volume). However this extra weight will not make much difference to the total weight of you, your bike/trike and the contents of the bag.

A disclaimer I have not used this bag. I have just read a description and looked at specifications.  The company has not paid me in any shape or form to publish this note. The photographs are reproduced by permission of B&W International.