Update 
I have accepted all valid criticisms of the stem model. Even though I tried to make the branches thicker and tested many types of supports, it was not enough.
Therefore, I made a new remixed model with my own self-modeled leaves. These are printed on the bed (unlike the old ones in the air) and positioned afterwards using heat.

I would like to thank you all for printing, sharing your pictures, and commenting.

Now, let me address the licensing and give proper credit to the original creators:

Rose (original) - The original model was made by marsmathofficial on Thingiverse and published under CC BY-NC-ND 4.0 DEED, which means the model can be shared and distributed in its original form. DO NOT SHARE REMIXED VERSIONS OF THIS MODEL
I am also sharing the original model; therefore, I am still respecting the CC BY-NC-ND license the original creator chose.

Stem (remixed) - The original model was made by Richard Tracy on Thingiverse and published under CC BY 4.0 DEED which means the model can be shared and distributed in its original form or remixed.

Base (original) - The original model was made by Richard Tracy on Thingiverse and published under CC BY 4.0 DEED which means the model can be shared and distributed in its original form or remixed.

Vase - That's mine, made through MakeMyVase on MakerLab, nothing extra about it.

Printing and processing instructions:

Rose - should print as it is, i personally like the silk pla look.

;New updated stem (flat leaves) has no printing issues;
Stem (old) - this is a tricky one, in an older post here by erin.wang, many had issues printing it. My remix addresses some of these by making the leaf stems thicker and painting custom supports, also, the stem is now longer and looks better in a vase. Print profile has fuzzy modifiers on leaves i personally like them that way.
Print instructions:
- use high-quality filament, which will prevent 90% of problems
- if you encounter any issues, manually set the print speed to 50% (this gives layers more time to cool down)
Post process instructions:
1. very carefully remove supports, start by small pieces from leaves and work your way down to the stem
2. carefully trim any excess material 
3. use heat to remove stringing (i used a cheap filament your results may be better) and carefully heat the branches under leafs
4. pose leaves to a more natural position while the branches are heated

Base - should print as it is, i personally like the fuzzy look.

Now something about the rose model, i made myself one modification to it. And that is the hole at the bottom so the final gluing would be easyer. Sadly i cannot share this model with you here or anywhere since the original creator forbids sharing of a remixed model. But i can give you quick instructions on how to do it yourself, that far CC BY-NC-ND cannot reach.
1. Export the model from bambu studio (File - Export - Export all objects as STL)
2. Import in Blender (File - Import - STL)
3. Go to edit mode
4. Select the inner most ring on the underside (use select circle an maneuver around)
5. Press “S” to scale down (move your mouse to scale, click to confirm)
6. Press “E” to extrude (move your mouse to extrude, click to confirm)
7. Export the model from blender (File - Export - STL)
8. Add model to the bambu studio in the original rose profile

Even better solution by @tweaqr

In Bambu Studio Right click on the rose --> Add nagitive part --> cylinder Click OK to the message box Select Scale from the top toolbar and set the size to 4mm,4mm,4mm Select Move from the top toolbar and set the position to X 0mm, Y 0mm, Z-15mm