Conclusion
Your rosacea symptoms may be alleviated by changing your diet to lower inflammation and enhance the health of your gut flora, along with an increase in antioxidant and pre/probiotic intake and a reduction in alcohol consumption.
Your rosacea symptoms could worsen if you consume hot meals, alcohol, or some fruits, vegetables, spicy foods, meats, or chocolate. To figure out which triggers apply to you, though, you must experiment.
References
[1] https://onlinelibrary.wiley.com/doi/pdf/10.1111/ijd.14757
[2] https://www.rosacea.org/patients/all-about-rosacea
[3] https://www.mayoclinic.org/diseases-conditions/rosacea/symptoms-causes/syc-20353815
[4] https://www.webmd.com/diet/supplement-guide-niacin