This rtl to tif conversion seems to be mainly related to attempts of exporting HP raster images (.rtl) to TIFF bitmap format (.tif, .tiff), something that can be doable using certain graphics editor or even dedicated picture conversion programs and online services.
Convert HP Raster Transfer Language bitmap image file to Aldus Tagged Image File Format (TIFF) bitmap image.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert rtl to tif on Windows
A CAD CGM converter
Convert from rtl file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.