GMLive relies on the fnames file (found in the runtime directory) for function and variable signatures, but this file is known to be occasionally unreliable, including this case

// # = constant
// * = readonly
// @ = instance variable
// & = obsolete
// $ = US spelling
// £ = UK spelling
// ! = disallowed in free
// % = property
// ? = struct variable
// ^ = do not add to autocomplete
// ^feature_flag = do not add to autocomplete if the feature flag is disabled
// [name] = optional argument

...

room
room_first*
room_last*
room_width*
room_height*

You can workaround this by adding the following to the end of obj_gmlive’s Create event:

gml_var_add("room_width", function(l_set,l_val){
	if(l_set){
		room_width = l_val;
		return undefined;
	} else return room_width;
});
gml_var_add("room_height", function(l_set,l_val){
	if(l_set){
		room_height = l_val;
		return undefined;
	} else return room_height;
});