In the following excerpt from Book 1, Part 20, a Sardaukar discusses Leto's capture with Dr. Yueh. The man utilizes simile to craft a consumption-centric image of the duke's capture:

Yueh glanced at Leto. “What about….”
“He’ll be delivered to the Baron all properly trussed like a roast for the oven.”

The narration compares the mode of Leto's delivery to the Baron to a roast entering into an oven. This figurative language draws on the imagery of excess and consumption that surround the Baron, in particular his outsized proclivity for food. In his greed, the Baron also seeks to consume Duke Leto. 

This instance of simile emblematizes several prominent motifs in the novel: that of greatness, excess, and consumption; along with that of animalistic imagery. As the Baron seeks to consume Duke Leto like a "roast," he simultaneously looks to consume everything over which the duke presides. Arrakis, the spice trade, the Fremen—all of these are synonymous with Duke Leto, under his purview within Dune's techno-feudalist system. This is yet another layer of the Baron's hedonistic overindulgence and greed, akin to his overconsumption of food.

In addition to drawing on the motif of consumption/excess, the above simile contends with animalistic behavior and comparison. By equating Duke Leto to a roast, the Sardaukar denigrates him to an inhuman position, placing him below Baron Harkonnen in the presumed natural hierarchy.