Should I be concerned about chemosis and rosacea with a lower blepharoplasty?

I've anecdotally seen rosacea patients have reactions to the absorbable suture used for the fat repositioning. It usually resolves on its own or with an injection after surgery. I give patients who I think may have this reaction the option to have permanent sutures placed instead, but most still prefer the absorbable suture. Again this is anecdotal.
Chemosis can occur in any patient after lower blepharoplasty and if it occurs, I typically address it very early on by placing a temporary tarsorrhaphy and with medical management.

First, rosacea has nothing to do with lower blepharoplasty unless you have an active infection related to it. If you are like most people your age and the "rosacea" is actually telangiectasia, there is no worry at all. Secondly, the only thing you need to do about guarding against chemosis (post operative edema of the sclera) is pick the surgeon who does the procedure very carefully, though, even in the best hands, it can occur. Fortunately lately it usually resolves on its own or with eyedrops. I rarely say this here, but you need to stop reading and trust your surgeon.