I think With Ella rose they same length and syllables can sound a hit choppy
What about:
Eliana rose
Elisa rose
Ella rosemary
Ella something rose
I know a few children called Scarlett rose. So it's v common combination I that bothers you
Scarlett theodora
Scarlett iris
Scarlett elsa
Scarlett does make me think Scarlett fever though! Sorry..