This is a weird bug. Below I include a script to reproduce.
When you extract a rar file with password means of "Right Click->Extract here", fileroller first does something like extracting and then it asks for the password and extracts files correctly. So it takes the double of time. Imagine extracting a dvd iso ^^. I think this bug continues in the last version because I didn't see any bug report about it.


---BOF---
echo "Proof of concept. Bug tested in file-roller 2.16.1"

#First we create 5 files
#Size is 20MB so you can refresh nautilus and see while they are extracted and deleted
echo "Creating 5 random files..."
dd if=/dev/urandom of=shit1 bs=20M count=1
dd if=/dev/urandom of=shit2 bs=20M count=1
dd if=/dev/urandom of=shit3 bs=20M count=1
dd if=/dev/urandom of=shit4 bs=20M count=1
dd if=/dev/urandom of=shit5 bs=20M count=1

#We pack them using password "test"
#I tried zip and rar. Only rar fails, maybe others?
#zip -1 -P test buggy shit*
echo "Packing them..."
rar a buggy shit* -ptest -m0


echo "Now try to uncompress buggy.rar with file-roller. right click button -> Extract here"
#file-roller extracts and deletes them one by one and when it has finished, now it ask for password and extracts correctly
#rm shit* buggy* -fr
---EOF---