Details

Description
sell sign with:
[sell]
64
fireworkrocket or firework_rocket
$1000

does not work, it says we do not have 64 rockets

Steps to reproduce
Place a sign
[sell]
64
fireworkrocket
$1000

Expected behavior
Sell items

Sell signs will not work if the item does not have the same item metadata.

I'm not sure why this was closed, is there then no way to buy/sell the rockets?

You can only sell firework rockets if they don't have any metadata. As far as I'm aware you can't obtain firework rockets without metadata in survival (they all have power even if there's no explosion effect iirc), so you can only sell firework rockets that have been spawned in through commands.