There is note in the Event description about deleting items:
Event Details
Rok & Lucy’s Fondest Heart will start after maintenance on December 11 and end on January 8, 2020 at 6:00 a.m. server time.
The following items will be removed from players’ inventories when the event ends on January 8.
Rok's Earnest Love Letter
The Fondest Heart
Box Filled with Lucy's Kindness
Shining Dragon Attribute Tonic (XP) (Event Version)
Freya's Wind Scroll (Event Version)
Freya's Ice Rose (Event Version)
After opening of Box Filled with Lucy's Kindness I've got Freya Rose and Wind scrolls that stacked with ones I have already had. Will all scrolls and roses disappear on January 8th?