whats wrong with my roses

[MarySRouthier]

I have just recently purchased a mini rose bush, Its still in the pot it origonally came in and I have it outside, For the first week or two it was blooming wonderfully and it looked beautiful, now the blooms are starting to look like they are dying, its been kept moist and I looked at the roots to see if they were overgrowing in the pot (going around in circles around the outside of the soil) and they arnt. What am I doing wrong, how can I fix it. Please help