Q: If members of the entrance procession are carrying something (a rose), do they reverence the altar or keep the procession moving?
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A: The GIRM’s description of the entrance procession allows the inclusion of “other ministers” (120, 172). I’m not sure what the function is of people carrying roses in the procession, but if they are doing so, then they do what other ministers do.
The ministers reverence the altar with a profound bow “when they have arrived at the sanctuary” (GIRM 49). I take this to mean that each minister reverences the altar upon arriving at the sanctuary and then moves into position. Many parishes have the custom of lining up all the ministers in the procession to bow together, but the GIRM never describes it that way. The procession of all the ministers keeps moving.
You can find more on the entrance procession in my book, Let Us Pray.