You can purchase roving and needlefelting needles on ebay. More and more yarn stores are selling these supplies.
Be very careful with your fingers and the needles as they are barbed.
Not recommended for children.
Use a large sponge or piece of foam as your "save your table" base, as you'll be poking and stabbing the roving into the cotton base sheet (or recycle your used fabric softener sheets, or just needlefelt your roving to itself).
As you can see I have a variety of needles, the more needles, the faster the landscape will come together, however single needles are good for details.