That same night they are to eat the meat roasted over the fire, along with bitter herbs, and bread made without yeast.
Vertically, the Israelites were commanded to make bread without yeast. Horizontally, it was happening this way:
31 During the night Pharaoh summoned Moses and Aaron and said, “Up! Leave my people, you and the Israelites! Go, ...
They are to eat [the lamb],
Verb - Qal - Imperfect - third person masculine plural | third person masculine singular
Strong's Hebrew 398: To eat
Does Numbers 9:11-12 assume the existence of the roasted lamb?
Yes, it is implied by the grammar and the context.
12 They shall not leave any of it until morning, nor break a bone of it;
Semantic range of etsem
Before anything else, let's look at the semantic range of etsem, which means "bone" or "skeleton". The first thing to notice is not just the similar sounding "tselem" (image) but the corresponding meaning of self or same. Bone (etsem) is used as a synechdoche for the person as a whole, containing their ...
Actually, John 19:36 about Jesus' bone being unbroken is a quotation from Ps 34:20 -
He protects all his bones; not one of them will be broken.
This is clearly interpreted as a Messianic prophecy by John.
However, Paul also tells us that Jesus was the anti-type of the Passover lamb:
John 1:29 - Behold the Lamb of God who takes away the sin of the world