Rhodophoria “Bearer of Roses” or Rosalia festivals were ancient Greek and Roman festivals to honor the dead, the military dead and various deities. It was also a spring festival about fertility and flowers so many Goddesses were honored during this time such as Aphrodite, Venus, Hathor, Aset, Isis and Isis-Aphrodite.
Some scholars think that a garland of roses may have been religiously associated with the Crown of Victory given to Wesir after his victory over death in the afterlife. Even though this was initially given to Heru, it was transferred to Wesir. Other gods associated with this festival are Heru and Ra. Other ways this occasion was celebrated was victory triumphing over enemies or protecting from harmful forces. During the Ptolemaic Period and later, the festival became more affiliated with Wesir’s mythos.
A long Rhodophoria festival (lasting 13 days) is listed on the Temple Festival Calendar of Soknopaiou Nesos which was dedicated to the crocodile God Sobek and Aset as both Aset/Isis Nepherses (with the Beautiful Throne) and Nephremmis (of the Beautiful Arms).
Wikipedia mentions that the dates to celebrate can last from May through July. If one were to move the start of the Ancient Egyptian calendar to another month (besides August–which is what I have done here) then the months would change (Mechir would be in February instead of January for instance).
Possible Dates to Celebrate:
2 Peret/Mechir/January
12 to 24-Festival of Roses/Rhodophoria
3 Peret/Pamenot/February
16 to 28-Rhodophoria
1 Shomu/Pachons/April
26-Festival of Roses/Rhodophoria
2 Shomu/Payni/May
May 9-13
Rhodophoria/Rosalia
May 13
Rhodophoria/Rosalia
May 31-June 1
Rhodophoria/Rosalia
Activities for this Festival
*Honor a God or Goddess associated with this festival
*Offer red roses on the shrine to the deity and/or the dead
*Make garlands of roses to put in your hair or drape around the shrine
*Offer red roses to the military or warrior dead in a shrine or at a graveyard
Other Posts about Rhodophoria from a few Years Back
From the House of Vines: Do You Want to Celebrate the Rhodophoria with Us?
A recap of rituals and posts from the House of Vines: Rhodophoria Recap
Sources:
J. Gwyn Griffiths. Apuleius of Madaurus: The Isis-Book: (Metamorphoses, Book XI) (Brill, 1975), pp 159–161.
Capron, Laurent. “Déclarations fiscales du Temple de Soknopaiou Nêsos: éléments nouveaux,” in Zeitschrift für Papyrologie und Epigraphik. Bd. 165, Dr. Rudolf Habelt GmbH, Bonn (Germany). (2008), pp. 142. 13 days.
Thomas-Perpillou, Francoise. Studia Hellenistica, Issue 31. (Centre National de la Recherche Scientifique, 1993), 127. From the Papyrus of Oxyrhynchos LII 3694. 12 day festival.
Hekster, Olivier. Rome and its Empire, AD 193-284. (Edinburgh University Press, 2008), 128. From the Feridale Duranum Calendar from the reign of Severus Alexander.
Wikipedia entry: Rosalia Festival
Fiercely Bright One 
…I feel less silly about buying fake roses to decorate Sobek’s shrine now. That’s cool.
That’s great! It’s awesome because in the ancient times, they’d put replicas or images of offerings if they didn’t have any on hand. So your roses (fake ones) are perfect as a perpetual offering. Kudos!
In case you wanted to know, the ones listed at Sobek and Aset’s Temple is
2 Peret/Mechir/January
12 to 25-Festival of Roses/Rhodophoria
I also found this one in the same article (but I’m not sure if it was on the Temple or not):
1 Shomu/Pachons/April
26-Festival of Roses/Rhodophoria
Hey there! This is my first visit to your blog! We
are a team of volunteers and starting a new initiative in a community in the same niche.
Your blog provided us valuable information to work on. You have done a extraordinary job!
Why, thank you! I’m glad the information was helpful.
Here is the correct source for one of the books listed above.
Perpillou-Thomas, Francoise. Fêtes d’Egypte ptolémaïque et romaine, d’après la documentation papyrologique grecque. (Studia Hellenistica Series 31). Peeters Publishers, 1993.