Why is the button disappearing?

import random
from tkinter import *

root = Tk()
root.geometry("700x500")         
root.title("rolling dice")

def roll():
    l1=Label(root,font=("times",200)) 
    faces=["\u2680","\u2681","\u2682","\u2683","\u2684","\u2685"]    
    l1.configure(text=f"{random.choice(faces)}{random.choice(faces)}")
    l1.pack()

b1 = Button(root,text="Lets roll", command=roll)
b1.place(x=340,y=0)             
root.mainloop()

If I mention the label l1 before def then it is doing what is expected, but I am not able to understand what is happening when I mention it inside def.