Summer eating can be defined by the cold summer rolls of Thai Spice (5117 Kelvin, 713-522-5100). Delicate and elegant, these loosely assembled rolls are magically light but complex. They are filling yet nutritious. Translucent rice paper swathes a scattering of warm peppery chicken, crunchy celery slivers, shaved cabbage, bright carrot shreds and yellow vermicelli threads. The kicker is the addicting sweet-and-sour dipping sauce, both tangy and spicy -- more balanced and tantalizing than the accompanying peanut sauce.