Can weigh be a linking verb?

Here's the sentence: The roast weighs four pounds.

Is the word weigh a linking verb?

First, let's consider the other option:

Weighs is an intransitive verb and four pounds is an adverb telling how much to roast weighs.

When a verb is modified by an adverb, it describes the action being done by the subject. Since the roast is not doing any action,  four pounds cannot be adverbial. If there were action here, then the verb would be transitive and not intransitive since it is followed by a noun. That is, four pounds would become the direct object. If this is confusing, consider this sentence: The butcher weighs the roast. Here, weighs is a transitive verb and roast is the direct object.

So, yes, in this sentence, weighs is best classified as a linking verb. Four pounds is an attribute of the roast. It is a four pound roast.