On the one hand, there is the desire for a well-kept garden free of weeds and, on the other hand, the need of roses for a nutrient-rich an well aerated soil. 

However, bark mulch, like wood chips, removes nutrients from the soil and contains tannins. As a result, the pH-level changes and the soil becomes asidic. Nitrogen is removed as the mulch decomposes, so you should only mulch if you know the pH-level of your garden soil well and can keep an eye on it. Depending on its condition, fertilizer should be added regularly. 

An alternative to bark mulch or wood chips is commercially available rose mulch. Also, use a rose fork to ensure good soil aeration, as this will allow the existing soil bacteria to provide active soil life. 

Speaking of which - we recommend pushing the bark mulch aside when piling in the fall. Then use garden soil or mature compost for the purpose.