The oil is Caligo Safewash Oil, here, https://handprinted.co.uk/products/caligo-safe-wash-oil and https://intaglioprintmaker.com/shop/caligo-safewash-oil-250ml or other printmaking suppliers listed under the Printmaking menu.
Normally you would print with dry paper for relief, but as Ling says in her reply, paper will be softer and more pliable if slightly damp, especially for the fish printing (or other awkwardly shaped objects!) Just a gentle sponge or spray will be enough.
Don’t spend a fortune on rollers! Plenty of economy options here https://intaglioprintmaker.com/category/economy-rollers and here https://handprinted.co.uk/collections/rollers.
Hope that helps…