Complex sentence: The only territories not returned were Empúries and Roussillon, which had already been granted to Sunyer I and Alaric respectively, and Urgell and Cerdanya, which had been detached from Toulouse by the usurper Aznar I Galíndez.
Split into simpler sentences: The only territories not returned were Empúries and Roussillon, which had already been passed to the Counts Sunyer I of Empúries and Alaric. In addition Urgell and Cerdanya, which had been separated from County of Toulouse by the usurper Aznar I Galíndez.