What are some creative stuff I could do with flowers my friend gave me?

Bundle them (if they aren’t already), tie a rope around the stems, and hang them upside down, to dry.
I have some thirty (birthday) roses like that, hanging from the ceiling in a corner of the room, and I am now in my forties.

All you have to do is tie them in a bundle .. hang them upside down and let them dry. I have lots of dry arrangements in my home. I never throw away roses.

I agree with the above suggestions. You can also make potpourrie out of them or sachets.

I have never done this so you would need to do some research into techniques and whether it would work for the flowers you have, but what about pressing the flowers and creating artworks you could frame?

You could laminate them. I don’t know if the hot lamination would damage the flowers. Try it with another flower first. They also make cold lamination sheets. They don’t seal as tight but should do the job. Press them in a book.

Wait for them to die…..then smoke them. :)

After enjoying them in a vase, save every petal and the centers of the blooms and the rose “hips” and lay them out to dry then use them in a sachet for your drawers or in a bowl in a room to spread some scent. Or even [as I did] with enough, fill a tiny zipped cotton pillowslip and put that in a decorative pillow cover and sleep with it. I have one that I use sometimes to rest under that special spot [achey or sexy] and sometimes to just lay across my face to smell and enjoy.