MARINATE THE CHICKEN: In a large bowl, mix the olive oil with the rosemary, thyme, oregano and ground cumin. Add the chicken and toss well. Cover and refrigerate for at least 2 hours or overnight.
MEANWHILE, MAKE THE HARISSA: In a small skillet, toast the cumin, coriander and caraway seeds over moderately high heat, shaking the skillet a few times, until the spices are fragrant, about 2 minutes. Transfer to a spice grinder and let cool completely. Grind to a powder.
In a blender, combine the roasted peppers with the chile, garlic, olive oil, lemon juice and ground spices and puree. Season the harissa with salt.
Light a grill. Thread the chicken pieces onto 8 metal skewers. Season with salt and grill over moderately high heat, turning, until nicely charred and just cooked, about 14 minutes. Serve the skewers with the harissa and hummus.
The harissa can be refrigerated for up to 5 days. Bring to room temperature before serving.