To prepare vinaigrette, whisk together mustard and vinegar until well incorporated, add shallots and while whisking constantly slowly add the olive oil until all is emulsified into the mustard. Season with salt and pepper, to taste. Set aside until needed. Combine the endives, pears, walnuts and Roquefort cheese in a medium bowl and toss. Place mixture in the middle of a plate and drizzle with vinaigrette. Serve immediately.