The 18-year-old Slovakian scored the winner for Chelsea's reserves on Monday night in a 3-2 win over Sunderland at Stamford Bridge.
The Slovakia under-21 international has joined Sean O'Driscoll's side following injuries to strike trio James Hayter, Billy Sharp and Ryan Mason.
Lalkovic will be in the Rovers squad for Saturday's game against Derby at Pride Park.
Source: Team Talk
Source: Team Talk