Heat grapeseed oil in a large nonstick frying pan on medium-high heat.
Add the endives to the pan and cook them for 1 to 2 minutes per side or until seared on both sides.
Add the sugar and cook until the endives are golden and caramelized.
Reduce heat to medium-low, add water and cover.
Cook the endives until fork tender, about 10 to 12 minutes.
Remove from heat and set aside to cool.
The endives may be cut in half again for serving or left as is.
Add the blood orange juice to a small saucepan and bring to a boil on high heat.
Turn heat down to low and gently simmer, stirring occasionally.
Reduce the juice until it becomes a syrup, about 10 minutes. Don’t let it reduce too far or the natural sugar will caramelize and burn.
Remove from heat and set aside.
When syrup has cooled, whisk in the lemon juice.
Season to taste with salt and freshly ground white pepper.
Peel the grapefruits, removing as much of the pith as possible, and cut evenly into 1/4-inch slices; you should get 5 to 6 slices from each grapefruit.
Overlap orange slices evenly in a circle on each of 4 plates.
On a separate plate, drizzle a bit of the blood orange jus over the endives, cover and microwave to warm up (depending on the microwave, 20 to 30 seconds).
Place the endives on top of the grapefruit slices.
Crumble some Roquefort on top of each salad and arrange the walnuts around the outsides of the plates.
Drizzle some blood orange jus over the salads and some olive oil around the plates.