One of the reasons I was so deeply attracted to Religio Romana was the attention that is given to the Dead and the Ancestors. In February, the end of the traditional Roman religious year, the month is spent paying our dues to those powers higher than us that perhaps we've neglected either knowingly or unknowingly. This shows up with the observation of the Parentalia and the Feralia within it, both to recognize the Lares, the God/Spirits of our more spiritually-developed Ancestors and Heroes, and the Manes, the Spirits of our Beloved Dead and, in my personal tradition, the Spirits of the Unclaimed Dead.
The month of May, a month of purification and possibly named after the Maiores (Ancestors), also has an ancient festival in it focusing on the Dead. But this time it is not for the Manes, the “good” Dead, those who had been given proper rites in burial and were offered cultus by their families, but the Lemures, the angry, restless Dead.