In a large pot, toast all of the spices over moderately high heat until fragrant, about 1 minute. Add the water, salt, brown sugar and bay leaves and bring to a boil, stirring to dissolve the salt and sugar. Pour the brine into a large roasting pan and let cool to room temperature. Put the pork roast in the brine, meaty side down. Cover the roasting pan and refrigerate overnight. Bring the pork roast to room temperature in the brine before roasting.
Preheat the oven to 350°. Set the pork roast on a large rimmed baking sheet, meaty side up. Roast the pork in the upper third of the oven for about 1 hour and 15 minutes, until an instant-read thermometer inserted in the thickest part registers 145°. Transfer the roast to a carving board; let rest for 15 minutes.
Using a small, sharp knife, peel the red grapefruit, removing all of the bitter white pith. Working over a large bowl, cut in between the membranes, releasing the grapefruit sections into the bowl.
In a small bowl, combine the orange juice, red wine vinegar, olive oil and honey; season the dressing with salt and pepper. Add the sliced fennel and red onion to the grapefruit sections in the large bowl.
Carve the pork roast into chops and transfer to plates. Toss the fennel salad with the dressing, mound the salad alongside the chops and serve.