Can my rotary hammer act as a hammer drill?
As a remodeling contractor, I've owned both hammer drills and rotary hammers.  The rotary hammers are frequently rated for drilling capacity by the diameter hole it can drill.  Most homeowner chores can be accomplished by 7/8 to 1" capacity.  You can drill larger holes, but at reduced speed.

There are 3 classes of SDS drills.  The widest range of bits are in the "SDS plus" sizes.  SDS max would be overkill.  

I have and use an SDS-to-1/2 chuck adapter, which is rated for concrete drilling.  I use it for the smaller sjzes only.

I would recommend getting a 3 function rotary hammer;
 - Drill only
 - Hammer only (useful with SDS chisels) and
 - Hammer + drill (my most used setting)