I bought a pack of wire on a roll because it was so much cheaper. There is no reason I can't use this, right? I figured I can just cover it with my floral tape and be good to go. Someone please let me know if that isn't true. Thanks

That will absolutely fine for flowers that won't be eaten ( most people don't ever eat gumpaste flowers, yuk!)  however, you cannot stick them directly into the cake.  You will need to either pop in coffee straws first, or if larger arrangement, use flower picks.

Yep, neither naked wire or floral tape should go directly into cake [naked wires rust and the glue on floral tape is not edible or food safe].  It's fine if they're stuck into straws or flower picks, though.

and it's hard to get it to stick -- hard to get the florist tape to cooperate -- not impossible but it's annoying enough for me that i wouldn't do flowers without wrapped wire -- so be prepared to invest a little more attention to that detail

I have used wire of a roll, as you said it is economical.I always store my florist tape in a ziplock bag so it doesn't dry out, and use straws in the cake to stick in.

yes i've used wire on a roll too but it was wrapped