"He's done a very professional job with them,” said Rohr of his counterpart. “Algeria were shaky at the time when we played them in World Cup qualifiers.
"We beat them 3-1 in Uyo and they made lots of individual errors and defensives mistakes that made it easier for us to win. They were also fragile in the 1-1 in Algeria
"Now I see a solid Algeria side with a good balance between attack and defence. They're still physical but they have come on since and the semi-final will be a much harder match than in World Cup qualifying."
Rohr’s men came from behind in the last 16 to beat Cameroon 3-2 and they scored a last minute winner to oust South Africa in the quarters.
"We still have things to improve, for example if we have chances to score a second goal we need to be more clinical," added Rohr. “But what I like about my players is that they never give up and it’s an attitude that can take us far.”
Nigeria are into the last four for the first time since they won the trophy in 2013 while Algeria have not played in a semi-final since 2010.
Their surge to the latter stages has been impressive. They won all their games in the group stages – including a 1-0 victory over tournament favourites Senegal – and conceded their only goal of the competition during the last eight stalemate against Cote d’Ivoire which they claimed in the penalty shoot-out.
“They've been more impressive than us on the whole so far," said Rohr. “We know they're a good side but we have a strong team too. We can reasonably hope to win based on our last two performances but we're wary because of our opponents.”
Belmadi, who took over as Algeria coach in August 2018, has been credited with extracting more consistency from skipper Riyad Mahrez.
The Manchester City midfielder has scored twice and laid on a goal during the competition.
Belmadi also has firepower off the bench. Adam Ounas highlighted his readiness with a brace after starting in the final Group C match against Tanzania and he was also on target as a substitute during the 3-0 last 16 romp past Guinea.
A first continental crown since 1990 is within sight.
"This is our target,” said Belmadi. “We want to write our history and the players want to write their history as well. It's not far. Two more steps but two very difficult steps to this great achievement. We will try our best."