The Germans suspect UEFA planned Champions League semifinal pairs before draw.
This is a match ticket in Rome where it shows the matches to be sold out (after Roma plays Lazio) and to pick up out of the two matches played at Olimpico of Roma.
Roma plays Genoa in 18
th April while here below you can see Roma playing Liverpool in 2th May 2018 which would technically mean for us we will face Real Madrid in the semifinals.
UEFA published that cover photo before the quarterfinal which would also make a suspicious pattern that quarterfinal Draw was riggied before it even started.