So it may have been the mattress they cut away that was rolled up instead of carpet.
Not likely. What was seen has the appearance of a rolled up carpet or rug, and a mattress wouldn't fit that appearance.
It's possible that it maybe could have been some sort of a thick tarp that they used to encase some something-or-other, and then rolled things up inside the tarp. In fact, the object has a lumpy appearance as if one or more items are enclosed. But on the outside, it sure looks like a carpet/rug. It sure doesn't look like a mattress to me.
Anyone that wants can see the object and decide. It's in the video at the top of this page multiple times. http://www.wsmv.com/story/26581181/investigators-search-house-of-suspect-in-holly-bobo-case
Sounds like the home has hardwood floors instead of carpet.
"Hardwood floors" and "large area rugs" are not mutually exclusive, and in fact are a fairly common floor treatment combo. They could have rolled up and taken a large oriental or persian wool rug, for example.