Is there a reason you can't just use roasting string and tie it in three places? That is what I have always done, especially when I stuff one with onions and sage. I just tie off the ends and tie it in the middle.
You could also use cheesecloth if you had nothing else.
Meanwhile, if you are intent upon containing your roast in netting, why not simply ask your butcher or meat department to wrap it for you?
Most shops will gladly do so at no additional charge.
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them