ů and ú are pronounced the same in czech /u:/ - the only difference is grammar. There are very obscure rules as when to to write ů or ú (wheter it's in the middle of the word, end of the word, exclamations etc...)
Slovak language also has ú and to my ears it's pronounced the same as in czech. ô is pronounced /uo/. It might be that the pronunciation has changed in czech language during hundreds of years. Same is the case of ä in slovak that used to have different pronunciation to a regular e but after many years (people being lazy) it is just being pronounced as a regular e.
So if we talk about pronunciation used these days then ů and ô are not pronounced the same at all.
I'm no historian/linguist. Born in slovakia studied in czech republic
EDIT: Thinking about it, kůň and kôň (horse) might be a better example